Geometric optical waveguide display system based on closely arranged microprisms

Abstract

The present invention relates to a geometric optical waveguide display system based on closely arranged microprisms, in which a light beam emitted by a light source enters the optical waveguide after being collimated by a collimation system, is reflected by the reflective surface of the optical waveguide and changes its angle to propagate in the optical waveguide in a large-angle total reflection manner, and when it contacts the microprism area at the light splitting area, a portion of the light passes through the glass plate and is reflected by the hypotenuse of the microprism, then enters the glass plate again through the light splitting area at a small angle and is emitted through the light emitting surface, and the remaining light beam continues to propagate backward to achieve pupil expansion. The microprism array for realizing pupil expansion function of the present invention is closely arranged, which can minimize unnecessary light beam spacing; the ratio of reflected and transmitted light is controlled by controlling the coating of different areas on the glass plate, thereby controlling the uniformity of the emitted light; the structure of the geometric optical waveguide is very simple, which overcomes the problems of complex structure and difficult process of other geometric waveguides, is convenient for one-time molding and assembly, and is easy for mass production.

Description

Technical Field

[0001] The present invention relates to the field of optical technology, and in particular to a geometric optical waveguide display system based on closely arranged microprisms. Background Art

[0002] The Head-Up Display (HUD) system is a type of airborne or vehicle-mounted instrument equipment with augmented reality functions. It projects driving parameters, navigation information, etc. in the form of images and characters directly in front of the driver through an optical system, allowing the driver to obtain various information from the aircraft and car while observing the driving environment.

[0003] With the rapid development of the automobile industry, the requirements for the integration of vehicle internal systems have been greatly increased, and the requirements for lightweight, miniaturization and display effects of HUD systems are getting higher and higher. The traditional vehicle-mounted HUD system is mainly designed according to the off-axis reflective structure. The image displayed by the image source is first projected onto the windshield or auxiliary display screen through the off-axis reflector system, and then reflected into the human eye. If this design scheme is used to achieve a large eye movement range and a large field of view, the volume of the reflector and the overall volume and weight of the system will be very large, and the system cannot be miniaturized and lightweight, and the vehicle cannot provide enough assembly space. The optical waveguide technology can expand the coupled-in beam into several coupled-out beams in a glass plate (this process is called pupil expansion). Applying it to the vehicle-mounted head-up display system can effectively reduce the volume of the optical machine system; and the beam after pupil expansion is generally parallel light, which is helpful for human eye observation. The beam angle will not change before and after pupil expansion, ensuring that the image will not be distorted. Therefore, the HUD system based on optical waveguide is widely regarded by the industry as an important direction for the next generation of HUD systems.

[0004] Optical waveguide display systems can be divided into geometric optical waveguides and diffraction optical waveguides according to the type of optical waveguides used. Diffraction optical waveguides achieve pupil expansion of light beams through diffraction elements (such as liquid crystal gratings, holographic gratings, etc.), but the diffraction angle and diffraction efficiency of diffraction elements are very sensitive to the wavelength of light, making it difficult to achieve full-color display.

[0005] Because geometric waveguide HUD can achieve system miniaturization and full-color display, it has received widespread attention in the application market. Geometric waveguide display technology abandons the complex optical system and large-size reflectors required in traditional design solutions, and completes image transmission and final imaging display through flat waveguides and embedded coupled input optical elements and coupled output optical elements. It has important application potential in achieving lightweight and miniaturized HUD systems. At the same time, it has no selectivity for the wavelength of light and is easy to achieve full-color display.

[0006] Geometric waveguides can be divided into transflective film waveguides and microprism waveguides according to the different coupling output optical elements. Among them, the transflective film waveguide uses multiple partially reflective mirrors (Partially Reflective Mirror, PRM) to control the coupling output of the light beam. Since each partial reflector must be embedded in the waveguide plate, it needs to be made in blocks and then glued into a whole in actual processing. The processing time is long and the cost is high. It is difficult to control the flatness of the entire waveguide during multiple gluing, and mass production is limited. The microprism waveguide controls the coupling output of the light beam through a microprism array; wherein, the microprism array is glued to the surface of the glass plate. Since the individual glass plate is simple to process and the microprism array is formed in one processing, it is highly suitable for mass production.

[0007] In some micro-prismatic optical waveguides, the ratio of reflected and transmitted light is controlled by controlling the different density arrangements of the micro-prism array, thereby controlling the uniformity of the emitted light. However, this will cause unnecessary intervals in the light beam, affecting the observation effect. Summary of the invention

[0008] In order to achieve the above-mentioned purpose and other advantages according to the present invention, the purpose of the present invention is to provide a geometric optical waveguide display system based on closely arranged microprisms, comprising a light source, a collimation system, and an optical waveguide; the optical waveguide comprises a glass plate and a microprism array, the microprisms in the microprism array are closely arranged, the glass plate is provided with a reflecting surface, a light emitting surface, an incident area, and a light splitting area, the light splitting area is located at microprism areas of the glass plate that are different along the propagation direction of the light, the microprism array is fixed on the light splitting area of ​​the glass plate, the reflecting surface is used to reflect the light beam incident from the incident area, the light splitting area is used to split the light that is totally reflected and propagated in the glass plate after the incident light is reflected by the reflecting surface, the light exiting surface is used to emit the light beam, the reflecting surface is adjacent to the light exiting surface and the surface where the incident area is located, the reflecting surface and the surface where the incident area is located form an acute angle, the reflecting surface and the light exiting surface form an obtuse angle, and the light exiting surface is opposite to the incident area and the light splitting area;

[0009] The light beam emitted by the light source enters the optical waveguide from the incident area after being collimated by the collimation system, is reflected by the reflection surface of the optical waveguide and changes its angle to propagate in a large-angle total reflection manner in the optical waveguide, and when it contacts the microprism area at the light splitting area, a portion of the light passes through the glass plate and is reflected by the hypotenuse of the microprism, then passes through the light splitting area at a small angle and enters the glass plate again and is emitted through the light exiting surface, and the remaining light beam continues to propagate backwards to achieve pupil expansion; wherein, the large angle means that it is greater than the total reflection critical angle corresponding to the waveguide, and the small angle is 0°±20°.

[0010] Further, the angle of the light beam emitted from the light emitting surface is consistent with the angle of the light beam incident into the optical waveguide.

[0011] Furthermore, the inclination angle of the microprism is

[0012]

[0013] Wherein, θ is the angle of the incident light beam, n1 is the refractive index of the glass plate, n2 is the refractive index of the microprism, α1 is the inclination angle of the glass plate, and α2 is the inclination angle of the microprism.

[0014] Furthermore, when the light splitting region on the glass plate splits the incident light at a large angle, the proportion of the reflected part gradually decreases from near to far along the propagation direction of the light beam.

[0015] Furthermore, the calculation formula for the transmittance of the spectral region at different regions of the glass plate along the light propagation direction is:

[0016]

[0017] Wherein, i=1, 2, ..., N; N is the total number of micro-prism regions; i represents the i-th micro-prism region.

[0018] Furthermore, the basic shape of a single microprism in the microprism array is a triangular pyramid.

[0019] Furthermore, each microprism constituting the microprism array is closely arranged without any spacing or the spacing distance does not exceed 1 / 10 of the side length of a single microprism.

[0020] Furthermore, the spectral film coated on the spectral region on the glass plate spectrally splits the incident light at a large angle according to a preset ratio, and has a transmittance greater than 90% for the incident light at a small angle.

[0021] Furthermore, the reflective surface on the glass plate is coated with a reflective film, which couples the incident light beam at a small angle into the optical waveguide at a large angle, so that the incident light beam propagates in the optical waveguide by total reflection.

[0022] Furthermore, when the refractive index of the glass plate is equal to the refractive index of the micro-prism, the angle between the reflection surface and the incident area is equal to the inclination angle of the micro-prism in the micro-prism array.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The geometric optical waveguide in the present invention includes a microprism array and a glass plate, and the microprism array is used to realize the pupil expansion of the light beam. The microprism array is composed of triangular prisms of the same size arranged closely and glued to one side of the glass plate. When the light beam propagates in the glass plate and contacts the microprism array area, part of the light beam passes through the glass plate and is reflected by the microprism to expand the pupil, and the remaining light beam continues to reflect and propagate in the glass plate. By controlling the energy ratio of the light beam transmitted and reflected in different areas of the glass plate, the energy of the pupil-expanding light beam in different areas can be evenly distributed.

[0025] The microprism array for realizing pupil expansion function of the present invention is closely arranged, which can reduce unnecessary light beam intervals to the greatest extent. At the same time, the ratio of reflected and transmitted light is controlled by controlling the coating of different areas on the glass plate, thereby controlling the uniformity of the emitted light.

[0026] The geometric optical waveguide in the present invention is composed of a glass plate and closely arranged microprisms, and has a very simple structure, which overcomes the problems of complex structure and difficult process of other geometric waveguides, is convenient for one-time molding and assembly, and is easy for mass production.

[0027] The present invention takes into account that the angle of light when propagating in the optical waveguide is large, generally greater than 40°, and when it contacts the coating surface, part of the light is transmitted and part of the light is reflected. When the transmitted light is reflected back to the coating surface through the microprism, the light angle is close to 0° and the transmittance is close to 100% after passing through the microprism with a properly designed angle. Through the appropriate film system design, the same coating surface can simultaneously meet the requirements of the light splitting of the propagating light beam in the optical waveguide and the anti-reflection of the pupil expansion light beam.

[0028] The present invention uses a microprism array as a coupling output optical element to construct a waveguide display system, and is expected to produce significant social and economic benefits in the airborne and vehicle-mounted fields in the future.

[0029] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present invention in conjunction with the accompanying drawings. The specific implementation of the present invention is given in detail by the following embodiments and their accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of this application. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0031] Figure 1 Schematic diagram of a geometric optical waveguide display system based on closely arranged microprisms according to Example 1.

[0032] In the figure: 1. glass plate; 11. reflection surface; 12. light emitting surface; 13. light splitting area; 14. incident area; 2. microprism array. DETAILED DESCRIPTION

[0033] The present invention is further described below in conjunction with the accompanying drawings and specific implementation methods. It should be noted that, under the premise of no conflict, the various embodiments or technical features described below can be arbitrarily combined to form a new embodiment.

[0034] Example 1

[0035] Geometric waveguide display systems based on closely arranged microprisms, such as Figure 1 As shown, it includes a light source for providing an input light beam, a collimation system for collimating the input light beam into a parallel light entering the light waveguide, and a light waveguide for realizing light beam pupil expansion; the light waveguide includes a glass plate 1 and a microprism array 2, the microprisms in the microprism array are closely arranged, the glass plate 1 is provided with a reflecting surface 11, a light emitting surface 12, a light splitting area 13, and an incident area 14, the light splitting area is located at microprism areas of the glass plate that are different along the propagation direction of the light, the microprism array is fixed on the light splitting area of ​​the glass plate, the reflecting surface is used to reflect the light beam incident from the incident area, the light splitting area is used to split the light that is totally reflected and propagated in the glass plate after the incident light is reflected by the reflecting surface, the light exiting surface is used to emit the light beam, the reflecting surface is adjacent to the light exiting surface and the surface where the incident area is located, the reflecting surface and the surface where the incident area is located form an acute angle, the reflecting surface and the light exiting surface form an obtuse angle, and the light exiting surface is opposite to the incident area and the light splitting area;

[0036] The light beam emitted by the light source is collimated by the collimation system and then enters the optical waveguide from the incident area. It is reflected by the reflection surface 11 of the optical waveguide and changes its angle to propagate in the optical waveguide in a large-angle total reflection manner. When it contacts the microprism area in the splitting area, a portion of the light passes through the glass plate and is reflected by the hypotenuse of the microprism. It then passes through the splitting area at a small angle and enters the glass plate again and is emitted through the light emitting surface. The remaining light beam continues to propagate backward, thereby achieving pupil expansion. Finally, the pupil-expanded light beam enters the human eye after propagating for a certain distance.

[0037] The above large angle means that it is greater than the critical angle of total reflection corresponding to the waveguide. The calculation formula of the critical angle of total reflection is: arcsin(n1 / n2), the angle between the light and the normal of the medium plane. Among them, n1 is the external refractive index of the medium, and n2 is the internal refractive index of the medium. Here, since the outside of the medium is air, n1 is 1. The refractive index of the medium is related to the material of the glass plate, and its refractive index ranges from 1.4 to 2.1. Usually, the critical angle of total reflection is about 40°, that is, the "large angle" mentioned here must be greater than 40°.

[0038] The above-mentioned small angle is relative to the large angle, which is generally less than 5° and will not exceed 20° at most.

[0039] Assume that the angle of the incident light beam is θ, the refractive index of the glass plate is n1, the refractive index of the microprism is n2, the inclination angle of the glass plate is α1, and the inclination angle of the microprism is α2. In order to make the angle of the outgoing light beam consistent with the incident light beam, then

[0040]

[0041] In particular, if the refractive index of the glass plate is equal to the refractive index of the microprism, that is, n1=n2, then α2=α1. In addition, considering that the incident light beam has a certain angular bandwidth during actual use, the microprism inclination angle α2 should be near the inclination angle corresponding to the center angle. Specifically, since the calculation formula of the microprism inclination angle α2 is related to the angle θ of the incident light beam, and the angle θ of the incident light beam has a certain bandwidth, the microprism inclination angle α2 calculated for different incident light beam angles that makes the output light beam angle unchanged is different (the change usually does not exceed 1°), and this angle is usually rounded (for processing convenience), so the actual output angle and the incident angle are inconsistent under certain incident angle conditions.

[0042] The spectroscopic film coated on the spectroscopic area on the glass plate splits the incident light at a large angle according to a certain ratio, ranging from a transmittance ratio of 0.05:0.95 to 1:0. It is possible to do so according to the actual use requirements. The transmittance of the incident light at a small angle is close to 100%, but it may not be 100% in reality. According to the processing level, the transmittance ranges from 90% to 99%, and is generally required to be greater than 95%. When the spectroscopic area on the glass plate splits the incident light at a large angle, the proportion of the reflected part (reflectance ratio transmission) gradually decreases from near to far along the propagation direction of the light beam, thereby achieving control of the uniformity of the pupil expansion beam illumination. By controlling the energy ratio of the light beam transmitted and reflected in different areas of the glass plate, the energy of the pupil expansion beam in different areas can be evenly distributed.

[0043] The micro-prismatic optical waveguide uses a micro-prism array as a coupling output optical element. Its advantage is not only that the micro-prism array is easy to process and produce in batches, but also that the energy ratio of the beam transmitted and reflected can be adjusted by adjusting the coating of the spectral area in different areas of the glass plate along the propagation direction of the light, and finally the energy of the pupil-expanding beam in different areas can be evenly distributed. The transmittance R of the spectral area in different areas is calculated as follows:

[0044]

[0045] Wherein, i=1, 2, ..., N; N is the total number of micro-prism regions; i represents the i-th micro-prism region.

[0046] In this embodiment, the microprism array is glued to the light-splitting area of ​​the glass plate, and the basic shape of a single microprism in the microprism array is a triangular pyramid, or close to this shape, or there is a slight change in this shape, such as one corner of the triangle is ground flat to become a quadrilateral, or becomes a rounded corner, etc. Each microprism constituting the microprism array is closely arranged without spacing or has a very small spacing due to actual processing limitations, which generally does not exceed 1 / 10 of the side length of a single microprism.

[0047] The microprism array for realizing pupil expansion function in the present invention is closely arranged, which can minimize unnecessary beam spacing. At the same time, the geometric optical waveguide in the present invention includes a glass plate and closely arranged microprisms, and has a very simple structure, which overcomes the problems of complex structure and difficult process of other geometric waveguides, and is easy to form and assemble in one step, and is easy to mass produce.

[0048] The reflective surface on the glass plate is coated with a reflective film, which couples the incident light beam at a small angle into the optical waveguide at a large angle, so that the incident light beam can propagate in the optical waveguide by total reflection, and the reflection ratio is close to 100%.

[0049] The angle between the reflection surface of the glass plate and the surface where the incident area is located is close to the inclination angle of the microprism in the microprism array; the refractive index of the glass plate is close to the refractive index of the microprism, ensuring that the angle of the pupil expansion beam is close to the original incident beam.

[0050] The difficulty of the geometric optical waveguide design of the present invention lies in how to achieve the same coating surface to simultaneously meet the requirements of the light splitting of the propagating light beam in the optical waveguide and the anti-transmission of the pupil expansion light beam. Considering that the light propagates in the optical waveguide at a large angle, generally greater than 40°, part of the light is transmitted and part of the light is reflected when it contacts the coating surface. When the transmitted light is reflected back to the coating surface through the microprism, the light angle is close to 0° and the transmittance is close to 100% after passing through the microprism with a properly designed angle; this coating requirement can be achieved through proper film system design.

[0051] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, commodity 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, commodity or device. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the process, method, commodity or device including the elements.

[0052] The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referenced to each other, and each embodiment focuses on the differences from other embodiments.

[0053] The above are only embodiments of this specification and are not intended to limit one or more embodiments of this specification. For those skilled in the art, one or more embodiments of this specification may have various changes and transformations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of one or more embodiments of this specification should be included in the scope of the claims of one or more embodiments of this specification.

Claims

1. A geometric optical waveguide display system based on closely arranged microprisms, characterized in that: The invention comprises a light source, a collimation system and an optical waveguide; the optical waveguide comprises a glass plate and a microprism array, the microprisms in the microprism array are closely arranged, the glass plate is provided with a reflecting surface, a light emitting surface, an incident area and a light splitting area, the light splitting area is located at microprism areas of the glass plate that are different along the light propagation direction, the microprism array is fixed on the light splitting area of ​​the glass plate, the reflecting surface is used to reflect a light beam incident from the incident area, the light splitting area is used to split the light beam that is totally reflected and propagated in the glass plate after the incident light is reflected by the reflecting surface, the light emitting surface is used to emit a light beam, the reflecting surface is adjacent to the light emitting surface and the surface where the incident area is located, the reflecting surface and the surface where the incident area is located form an acute angle, the reflecting surface and the light emitting surface form an obtuse angle, and the light emitting surface is opposite to the incident area and the light splitting area; The light beam emitted by the light source enters the optical waveguide from the incident area after being collimated by the collimation system, is reflected by the reflection surface of the optical waveguide and changes its angle to propagate in the optical waveguide in a large-angle total reflection manner, and when it contacts the micro-prism area at the light splitting area, a portion of the light passes through the glass plate and is reflected by the hypotenuse of the micro-prism, then passes through the light splitting area at a small angle and enters the glass plate again and is emitted through the light exiting surface, and the remaining light beam continues to propagate backwards, thereby achieving pupil expansion; wherein the large angle means a value greater than the critical angle of total reflection corresponding to the waveguide, and the small angle is 0°±20°; When the light splitting area on the glass plate splits the incident light at a large angle, the proportion of the reflected part gradually decreases from near to far along the propagation direction of the light beam; The spectral film coated on the spectral region on the glass plate spectrally splits the incident light at a large angle according to a preset ratio, and the transmittance of the incident light at a small angle is greater than 90%; The calculation formula of the transmittance of the split light area in different areas of the glass plate along the light propagation direction is: Wherein, i=1, 2, ..., N; N is the total number of micro-prism regions; i represents the i-th micro-prism region.

2. The geometric optical waveguide display system based on closely arranged microprisms according to claim 1, characterized in that: The angle of the light beam emitted from the light emitting surface is consistent with the angle of the light beam incident into the optical waveguide.

3. The geometric optical waveguide display system based on closely arranged microprisms according to claim 2, characterized in that: The inclination angle of the microprism is Wherein, θ is the angle of the incident light beam, n1 is the refractive index of the glass plate, n2 is the refractive index of the microprism, α1 is the inclination angle of the glass plate, and α2 is the inclination angle of the microprism.

4. The geometric optical waveguide display system based on closely arranged microprisms according to claim 1, characterized in that: The basic shape of a single microprism in the microprism array is a triangular pyramid.

5. The geometric optical waveguide display system based on closely arranged microprisms according to claim 4, characterized in that: Each microprism constituting the microprism array is closely arranged without any spacing or the spacing distance does not exceed 1 / 10 of the side length of a single microprism.

6. The geometric optical waveguide display system based on closely arranged microprisms according to claim 1, characterized in that: The reflective surface on the glass plate is plated with a reflective film, which couples a small-angle incident light beam into the optical waveguide at a large angle, so that the incident light beam propagates in the optical waveguide by total reflection.

7. The geometric optical waveguide display system based on closely arranged microprisms according to claim 1 or 3, characterized in that: When the refractive index of the glass plate is equal to the refractive index of the micro-prism, the angle between the reflection surface and the incident area is equal to the inclination angle of the micro-prism in the micro-prism array.

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