Vehicle-mounted imaging device based on MEMS array

Abstract

The application discloses a vehicle-mounted imaging device based on a MEMS array, comprising: a light source for emitting a plurality of parallel light groups into a rough light beam; a MEMS micro-mirror array mechanism for reflecting the rough light beam emitted by the light source at a certain angle; and an imaging lens having a positive focal length for converging the light beam reflected by the MEMS micro-mirror array mechanism into a real image, or having a negative focal length for diverging the light beam reflected by the MEMS micro-mirror array mechanism into a virtual image. The application has the advantages that: through cooperation of the parallel rough light beam light source and the MEMS micro-mirror array mechanism, a large eyebox range can be observed without a screen, and compared with a single MEMS micro-mirror, the MEMS micro-mirror array mechanism can further reduce the space occupied by the MEMS part, thereby achieving the purpose of a small volume and a large field of view.

Description

Technical Field

[0001] The invention relates to a vehicle-mounted imaging device based on a MEMS array. Background Art

[0002] The on-board aerial imaging device, abbreviated as AID, is different from the conventional head-up display device HUD. The imaging of HUD is generally located on the outside of the car's front windshield, and the image is virtual in the direction of the human eye. The AID device is designed to form a real image between the car's front windshield and the driver and passengers. In addition to displaying content, it can also cooperate with gesture recognition and other devices for human-computer interaction.

[0003] HUDs and AIDs are used in the front instrument panel of a car, improving the driver's interaction with the instrument panel. This significantly reduces the number of times the driver has to look down to check the instrument panel, particularly during high-speed driving, thereby improving safety. However, HUDs and AIDs should be presented in a way that does not obstruct the driver's view. Solutions like HUDs or other diffuser screens are not as safe.

[0004] The installation of HUDs and AIDs requires a certain amount of space. The larger the image size, the larger the space occupied. In automotive HUD and AID scenarios, the limited space on the dashboard restricts the image size of HUD and AID devices. Within the limited space on the dashboard, there is limited vertical clearance, but more horizontal clearance. Therefore, the future trend is for HUD and AID devices on the dashboard to be flatter.

[0005] Existing aerial imaging equipment, based on air projection technology, mainly includes:

[0006] 1. The first method is the negative refraction plate method, which uses a negative refraction plate to reconstruct an equal-sized real image in the air with the help of reflection from the inner surface of the car's windshield.

[0007] 2. The second method is the medium "screen" method, which sets a scattering surface (such as a projection screen) at the imaging position to scatter the image formed by the projection light machine and then scatter it to the human eye;

[0008] 3. The third reflective solution, similar to the head-up display (HUD), uses a free-form reflective lens to form a real image.

[0009] 4. The fourth type is an imaging solution based on a tiny MEMS array.

[0010] For the first type of negative refraction plate, such as Figure 1As shown, the real image 4 and the image source 1 are mirror images about the negative refractive plate 8. When viewed from the eyebox 5, the line of sight generally extends to the negative refractive plate, resulting in partial obstruction. The first approach to addressing this obstruction is to increase the angle between the line of sight and the normal to the negative refractive plate, while also aligning the negative refractive plate as closely as possible to the vehicle's dashboard. This approach requires a significant increase in the area of ​​the negative refractive plate, easily exceeding 1 meter in length, making it impractical. The second approach to addressing this obstruction is to use the vehicle's windshield for a single reflection. However, the distance between the windshield and the dashboard is typically 250-300 mm. Because the negative refractive plate has a magnification of only 1, the image source is far from the plate, resulting in a larger system. In this scenario, a virtual image is formed outside the windshield, rather than a real image. Furthermore, due to the technical characteristics of the negative refractive plate imaging method, significant stray light is present. Furthermore, image quality cannot be as detailed, and the quality of the image depends on the spacing of the reflective arrays within the negative refractive plate.

[0011] The second medium "screen" approach utilizes a layer of medium to scatter light, allowing the projected light to be visible within a wide range of the eyebox at a smaller aperture angle. This approach is only applicable in special circumstances where image transparency is not required. However, aerial intelligent imaging equipment based on the front instrument panel of a vehicle requires an unobstructed image, which makes projection screens and aerial water curtains impractical for real-world applications.

[0012] In addition, Figure 2 The figure shown in the figure also represents a conventional solution. The image source 7 is composed of a two-dimensional array of pixels. Common image sources include transmissive LCD screens, reflective LCOS screens, and DMD chips. After passing through the imaging lens 3 or the reflective system, the image source reproduces an enlarged or reduced real image 4 at a specific location. When the human eye views the image at the eye box 5, there is a requirement for the observation area. This requires that each pixel on the image source has a certain luminous aperture angle. The light emission of the pixel is achieved by backlighting, so the backlight source must have a certain luminous angle. If the illumination is a single-angle flat light, observation within a certain area cannot be achieved. Of course, the light can be dispersed by adding a diffusion film behind the flat light, but in essence, the illumination beam irradiating the image source must be divergent light.

[0013] like Figure 3 As shown, a small volume solution based on two-dimensional MEMS 10 is provided. Because a thin light beam 11 is used for imaging, the combination of two-dimensional MEMS 10 and laser light source 9 can achieve a very small volume itself, but a screen 12 with a scattering function must be used to achieve viewing at different positions.

[0014] For the third type of reflection method, similar to head-up displays (HUDs), the processing precision of free-form surface reflectors is generally required to be high. The field of view of this solution is generally limited to approximately 12×3°. A larger field of view requires a larger optical aperture. In addition, this solution also faces the problem of sunlight stray light. The reflectivity of the reflector must be above 85%, and any stray light is more easily detected by the human eye. This solution is also generally larger in size.

[0015] For the fourth imaging solution based on a tiny MEMS array, such as the "Spatial Imaging Device" disclosed in publication number CN109254410A, a design concept that achieves flatness is proposed based on the nature of human vision. Based on the technical characteristics of this solution, we also found some limitations of this solution. First, considering the diameter of the human pupil, which is generally distributed between 2 and 8 mm, if there is no image loss in the observation area, the MEMS array needs to be very dense. The larger the ratio of the distance between the observation area and the display area to the distance between the MEMS array and the display area, the denser the MEMS array. In the case of large-scale imaging, the number of MEMS will be very large. Second, considering the imaging resolution requirements, the different directions of light rays forming the image point in the air must have a small enough beam diameter. Third, the number of optical fibers is the same as the number of MEMS array units. Considering the resolution requirements, this number is extremely large. Summary of the Invention

[0016] The object of the present invention is to provide a vehicle-mounted imaging device based on a MEMS array, which can effectively solve the problems of large size and small field of view of existing vehicle-mounted imaging devices.

[0017] In order to solve the above technical problems, the present invention is implemented through the following technical solutions: a vehicle-mounted imaging device based on a MEMS array, comprising:

[0018] Light source: used to emit multiple beams of parallel light to form a coarse light beam;

[0019] MEMS micro-mirror array mechanism: reflects the coarse light beam emitted by the light source;

[0020] Imaging lens: has a positive focal length, used to converge the light beam reflected by the MEMS micro-vibration mirror array mechanism to form a real image; or has a negative focal length, used to diverge the light beam reflected by the MEMS micro-vibration mirror array mechanism to form a virtual image.

[0021] Preferably, at least one beam splitter is provided on the optical path between the light source and the MEMS micro-vibration mirror array mechanism.

[0022] Preferably, a beam splitter is provided on the optical path between the light source and the MEMS micro-vibration mirror array mechanism, and a portion of the coarse light beam emitted by the light source is reflected onto the MEMS micro-vibration mirror array mechanism through the beam splitter, and another portion of the coarse light beam passes through the beam splitter.

[0023] Preferably, the beam splitter has a transmittance of 50% and a reflectivity of 50%.

[0024] Preferably, two parallel beam splitters are provided on the optical path between the light source and the MEMS micro-vibration mirror array mechanism, namely a first beam splitter and a second beam splitter. A portion of the coarse light beam emitted by the light source is reflected onto the MEMS micro-vibration mirror array mechanism through the first beam splitter, and another portion of the coarse light beam is irradiated onto the second beam splitter through the first beam splitter. A portion of the coarse light beam irradiated onto the second beam splitter is reflected onto the MEMS micro-vibration mirror array mechanism, and the other portion is transmitted through the second beam splitter.

[0025] Preferably, the transmittance of the first beam splitter is 75%, and the reflectance is 25%; the transmittance of the second beam splitter is 50%, and the reflectance is 50%.

[0026] Preferably, the MEMS micro-vibration mirror array mechanism includes a plurality of MEMS micro-vibration mirrors arranged in a rectangular array.

[0027] Preferably, the imaging lens has a positive focal length, and the imaging lens is a Fresnel lens or a Fresnel lens group.

[0028] Preferably, the imaging lens has a negative focal length, and the imaging lens is a concave lens or a combination of a concave lens and one or more lenses.

[0029] Preferably, the light beam emitted by the light source is a monochromatic light beam, or the light beam emitted by the light source is a mixed light beam of three colors: R, G, and B.

[0030] Compared with existing technologies, the present invention offers the following advantages: when the imaging lens has a positive focal length, a real image is formed, enabling aerial imaging and facilitating human-computer interaction; when the imaging lens has a negative focal length, a virtual image is presented, serving as a head-up display (HUD). By combining a coarse parallel beam light source with a MEMS micro-mirror array mechanism, a wide eyebox viewing area can be achieved without a screen. Furthermore, the use of a MEMS micro-mirror array mechanism further reduces the space occupied by the MEMS component compared to a single MEMS micro-mirror, achieving a compact size with a large field of view. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a schematic diagram of the existing negative refraction plate form;

[0032] Figure 2 This is a schematic diagram of the existing aerial imaging principle;

[0033] Figure 3 This is the schematic diagram of the existing two-dimensional MEMS solution;

[0034] Figure 4This is a schematic diagram of a first embodiment of a vehicle-mounted imaging device based on a MEMS array of the present invention using a positive focal length imaging lens;

[0035] Figure 5 Schematic diagram of the structure of the MEMS micro-mirror array mechanism used in the MEMS array-based vehicle-mounted imaging device of the present invention;

[0036] Figure 6 This is a schematic diagram of a second embodiment of the present invention, in which a vehicle-mounted imaging device based on a MEMS array adopts a positive focal length imaging lens;

[0037] Figure 7 This is a schematic diagram of a third embodiment of the present invention, in which a vehicle-mounted imaging device based on a MEMS array adopts a positive focal length imaging lens.

[0038] Figure 8 This is a schematic diagram of a fourth embodiment of a vehicle-mounted imaging device based on a MEMS array according to the present invention, when a negative focal length imaging lens is used.

[0039] The figures are marked as follows: light source 1, MEMS micro-vibration mirror array mechanism 2, MEMS micro-vibration mirror 21, imaging lens 3, real image 4, eye box 5, beam splitter 6, first beam splitter 61, second beam splitter 62, image source 7, negative refraction plate 8, laser light source 9, two-dimensional MEMS 10, fine beam 11, screen 12, virtual image 13. DETAILED DESCRIPTION

[0040] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to be used to explain the present invention, but should not be understood as limiting the present invention.

[0041] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0042] Example 1:

[0043] See Figure 4 、 Figure 5This is an embodiment of the vehicle-mounted imaging device based on a MEMS array of the present invention. The vehicle-mounted imaging device based on a MEMS array includes: a light source 1, a MEMS micro-vibration mirror array mechanism 2 and an imaging lens 3. The light source 1 is used to emit a coarse light beam composed of multiple beams of parallel light, which are irradiated on the MEMS micro-vibration mirror array mechanism 2 at an inclined angle, and the light beam emitted by the light source 1 covers the entire surface of the MEMS micro-vibration mirror array mechanism 2. Each MEMS micro-vibration mirror 21 in the MEMS micro-vibration mirror array mechanism 2 can independently control the reflection angle. The imaging lens 3 has a positive focal length, and is reflected by the MEMS micro-vibration mirror array mechanism 2 into multiple beams of parallel light, which are then converged by the imaging lens 3 to form a real image 4 in the air. As long as the user is in the area covered by the eye box 5, the complete real image 4 can be viewed.

[0044] The MEMS micro-vibration mirror array mechanism 2 is composed of a plurality of MEMS micro-vibration mirrors 21 spliced ​​in a rectangular array. The arrangement of the MEMS micro-vibration mirrors 21 is not limited to Figure 5 The given form is not limited to the size of a single MEMS unit, and is specifically determined according to the refresh frequency of the MEMS micro-vibration mirror 21 and the angular deflection accuracy.

[0045] Imaging lens 3 can be a single Fresnel lens or a Fresnel lens assembly. Leveraging the thinness of the Fresnel lens, the overall device size and weight can be further reduced. The MEMS micro-mirror array mechanism 2 modulates incident parallel light into parallel light at different angles. Parallel light at one angle ultimately forms a real image point in mid-air after passing through imaging lens 3. The MEMS array then reconstructs a single image in mid-air by modulating the incident parallel light into different angles.

[0046] If only a monochrome image is required to be displayed, the light beam emitted by the light source 1 is a monochrome light beam. If a color image is required to be displayed, the light source 1 can use a mixed light beam of R, G, and B colors.

[0047] The larger the angle between the light source 1 and the surface normal of the MEMS micro-vibration mirror array mechanism 2, the smaller the spacing between the imaging lens 3 and the MEMS micro-vibration mirror array mechanism 2 can be, which can effectively shorten the volume of the system. However, the larger the normal angle, the smaller the size requirement of the MEMS micro-vibration mirror 21, and the more MEMS micro-vibration mirrors 21 are needed. Therefore, the appropriate normal angle between the light source 1 and the MEMS micro-vibration mirror array mechanism 2 should be selected based on the actual cost.

[0048] By cooperating with a light source 1 of parallel coarse light beam and a MEMS micro-mirror array mechanism 2, a large eye box 5 range viewing can be achieved without a screen. Moreover, the use of the MEMS micro-mirror array mechanism 2 can further reduce the space occupied by the MEMS compared to a single MEMS, thereby achieving the goal of a small volume and a large field of view.

[0049] Example 2:

[0050] like Figure 6 As shown, the difference from Example 1 is that a beam splitter 6 is added between the light source 1 and the MEMS micro-vibration mirror array mechanism 2. The surface of the beam splitter 6 is coated so that the light incident on the beam splitter 6 is 50% transmitted and 50% reflected at the first incident surface. The second incident surface of the beam splitter 6 is also coated with an anti-reflection coating to maximize the transmission of light. The first incident surface of the beam splitter 6 has a 50% transmission and 50% reflection, which maximizes the utilization of light.

[0051] The coarse light beam emitted by the light source 1 is irradiated onto the beam splitter 6 and reflected by the beam splitter 6 to the MEMS micro-mirror array mechanism 2. Each MEMS micro-mirror 21 in the MEMS micro-mirror array mechanism 2 can individually adjust the reflection angle to form multiple beams of parallel light. After passing through the beam splitter 6, they are converged by the imaging lens 3 to form a real image 4. As long as the user is in the area covered by the eye box 5, the complete real image 4 can be viewed.

[0052] Example 3:

[0053] like Figure 7 As shown, the difference from Example 1 is that two beam splitters 6 are added between the light source 1 and the MEMS micro-mirror array mechanism 2. After the two beam splitters 6 are added, the distance between the imaging lens 3 and the MEMS micro-mirror array mechanism 2 can be reduced, and the incident aperture of the light source 1 can also be reduced, which can significantly reduce the volume of the system.

[0054] Two beam splitters 6 are arranged in parallel, with the first beam splitter 61 close to the light source 1 and the second beam splitter 62 away from the light source 1. Part of the light emitted by the light source 1 is reflected by the first beam splitter 61 onto the MEMS micro-vibration mirror array mechanism 2, and the other part is irradiated by the first beam splitter 61 onto the second beam splitter 62. Part of this part of the light passes through the second beam splitter 62, and the other part is reflected by the second beam splitter 62 onto the MEMS micro-vibration mirror array mechanism 2. The light beam reflected from the MEMS micro-vibration mirror array mechanism 2 will pass through the first beam splitter 61 and / or the second beam splitter 62, and then converge into a real image 4 through the imaging lens 3. The complete real image 4 is finally viewed by the user within the range of the eye box 5. The transmittance of the first beam splitter 61 is 75%, and the reflectivity is 25%; the transmittance of the second beam splitter 62 is 50%, and the reflectivity is 50%, which maximizes efficiency and uniform brightness.

[0055] With the use of the beam splitter 6 in the second and third embodiments, there is no size restriction on the size of individual MEMS mirrors 21 in the MEMS mirror array mechanism 2. As long as the effective spacing between the MEMS mirrors 21 is small enough to ensure that there is no image loss at different viewing positions, the number of MEMS mirrors can be reduced. Of course, three or more beam splitters 6 can also be used to further reduce the system size.

[0056] Example 4

[0057] like Figure 8 As shown, the difference from Examples 1, 2, and 3 is that the imaging lens 3 has a negative focal length. Therefore, the light beam reflected from the MEMS micro-mirror array mechanism 2 will diverge after passing through the imaging lens 3, forming a virtual image 13 on the side of the imaging lens 3 located on the MEMS micro-mirror array mechanism 2. The imaging lens 3 can be a single concave lens or a combination of a concave lens and a convex lens, as long as the focal length of the entire imaging lens 3 is negative, thereby realizing the HUD function.

[0058] Compared with conventional MEMS solutions, the above solution eliminates the screen because the coarse beam illumination can form a large beam aperture that is suitable for human viewing. Compared with conventional negative refractive flat panels and similar HUD solutions, the use of coarse beam illumination and a beam splitter 6 structure can significantly reduce the system volume, achieving a smaller volume and a larger field of view.

[0059] The above description is only a specific embodiment of the present invention, but the technical features of the present invention are not limited thereto. Any changes or modifications made by any technician in this field within the scope of the present invention are included in the patent scope of the present invention.

Claims

1. A vehicle-mounted imaging device based on a MEMS array, characterized by: include: Light source: used to emit multiple beams of parallel light to form a coarse light beam; MEMS micro-mirror array mechanism: reflects the coarse light beam emitted by the light source; Imaging lens: has a positive focal length, used to converge the light beam reflected by the MEMS micro-vibration mirror array mechanism to form a real image; or has a negative focal length, used to diverge the light beam reflected by the MEMS micro-vibration mirror array mechanism to form a virtual image; A beam splitter is also provided on the optical path between the light source and the MEMS micro-mirror array mechanism. Part of the coarse light beam emitted by the light source is reflected by the beam splitter onto the MEMS micro-mirror array mechanism, and the other part of the coarse light beam passes through the beam splitter. The MEMS micro-vibration mirror array mechanism includes a plurality of MEMS micro-vibration mirrors arranged in a rectangular array.

2. The vehicle-mounted imaging device based on a MEMS array according to claim 1, wherein: The beam splitter has a transmittance of 50% and a reflectivity of 50%.

3. The vehicle-mounted imaging device based on a MEMS array according to claim 1, wherein: Two parallel beam splitters are also provided on the optical path between the light source and the MEMS micro-vibration mirror array mechanism, namely the first beam splitter and the second beam splitter. Part of the coarse light beam emitted by the light source is reflected onto the MEMS micro-vibration mirror array mechanism through the first beam splitter, and the other part of the coarse light beam is irradiated onto the second beam splitter through the first beam splitter. Part of the coarse light beam irradiated onto the second beam splitter is reflected onto the MEMS micro-vibration mirror array mechanism, and the other part is transmitted through the second beam splitter.

4. The vehicle-mounted imaging device based on a MEMS array according to claim 3, wherein: The transmittance of the first beam splitter is 75%, and the reflectance is 25%; the transmittance of the second beam splitter is 50%, and the reflectance is 50%.

5. The vehicle-mounted imaging device based on a MEMS array according to claim 1, wherein: The imaging lens has a positive focal length and is a Fresnel lens or a Fresnel lens group.

6. The vehicle-mounted imaging device based on a MEMS array according to claim 1, wherein: The imaging lens has a negative focal length and is a concave lens or a combination of a concave lens and one or more lenses.

7. The vehicle-mounted imaging device based on a MEMS array according to claim 1, wherein: The light beam emitted by the light source is a monochromatic light beam; or, the light beam emitted by the light source is a mixed light beam of three colors: R, G, and B.

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