A compact collimating system for waveguides and applications thereof

Abstract

This invention discloses a compact waveguide collimation system and its application. The system, along the optical axis, sequentially includes a first lens group, an aperture stop, a second lens group, a prism-equivalent lens, a window protective sheet, and an image plane position. The first lens group effectively corrects aberrations and chromatic aberrations through a combination of a double-layered positive power meniscus lens and a cemented lens. The second lens group uses a negative power biconcave lens for beam expansion combined with a symmetrical lens structure to reduce the difficulty of aberration correction. The system uses spherical mirrors and glass materials throughout. By optimizing the optical power, surface shape, and relative positions, it achieves high collimation, high relative illumination, low distortion, compact structure, and low cost, making it suitable for optical waveguide display systems.

Description

Technical Field

[0001] This invention relates to a compact waveguide collimation system and its application, primarily used as a collimation element in optical waveguide displays. Background Technology

[0002] Optical waveguide technology uses a dielectric substrate to cause total internal reflection of light input under certain conditions within the waveguide. Specific optical elements are then used to control the direction and intensity of the light, ultimately projecting an image onto a display surface. Due to its excellent display effects and performance characteristics, optical waveguide technology holds promise for future applications in AR glasses, head-up displays, tablet computers, and other fields.

[0003] Optical waveguide technology can be divided into geometric waveguides and diffractive waveguides. Both require parallel light to be input at a certain angle through an inlet coupling grating. After modulation by the inlet coupling grating, the light undergoes total internal reflection within the waveguide for transmission, and finally, the image is achieved through the exit pupil via an outlet coupling grating. The key factor in the imaging quality of a waveguide system lies in the imaging quality of the collimation system. Therefore, the design of the collimation system is crucial in optical waveguide display systems. Simultaneously, the design of the collimation system needs to comprehensively consider factors such as the optomechanical type, the size of the light wave inlet coupling, and the waveguide display field of view. The ideal collimation system is expected to be compact, cost-effective, and possess high imaging quality. Therefore, designing a compact, cost-effective, and high-quality collimating lens is one of the key challenges in optical design in this field. Summary of the Invention

[0004] Purpose of the invention: In view of the above-mentioned background, a compact collimation system for waveguides is proposed, which can be used to generate collimated light in waveguide systems. While meeting the requirements of high imaging quality, it effectively reduces lens costs. At the same time, the compact design simplifies the optical components of the system and reduces the optical volume of the system.

[0005] Technical solution: A collimation system for a compact waveguide, which includes, along the optical axis from the object side to the image side, a first lens group, an aperture, a second lens group, a prism equivalent lens, a window protection sheet, and an image plane position;

[0006] The first lens group includes a first lens, a second lens, a third lens, and a fourth lens; wherein,

[0007] The first lens is a meniscus lens with positive optical power;

[0008] The second lens is a meniscus lens with positive optical power;

[0009] The third lens is a biconcave lens with negative optical power, which together with the fourth lens forms a cemented lens;

[0010] The fourth lens is a biconvex lens with negative optical power;

[0011] The second lens group includes a fifth lens, a sixth lens, a seventh lens, and an eighth lens; wherein,

[0012] The fifth lens is a biconcave lens with negative optical power;

[0013] The sixth lens is a meniscus lens with positive optical power;

[0014] The seventh lens is a biconvex lens with positive optical power;

[0015] The eighth lens is a biconvex lens with positive optical power.

[0016] Furthermore, all lenses in the first and second lens groups are spherical mirrors.

[0017] Furthermore, the lens materials in the lens group are all optical glass, with a refractive index ranging from 1.45 to 1.85 and an Abbe number ranging from 20 to 80.

[0018] Furthermore: the object-side light rays are incident as parallel light, and are focused by the collimation system onto the image plane, with the diameter of the focused spot at the image plane being less than 10 micrometers.

[0019] Furthermore, the equivalent focal length (F0) of the projection lens, the focal length (F1) of the first lens group, and the focal length (F2) of the second lens group satisfy the following relationship:

[0020] 1.5 < |F1 / F0| < 2.5;

[0021] 1.5 < |F2 / F0| < 2.5.

[0022] Furthermore, the back working distance (BFL) of the projection lens and the equivalent focal length (F0) satisfy the following relationship:

[0023] |BFL / F0|>3.

[0024] Furthermore, the incident and exit surfaces of the prism-equivalent lens are both planar, and the ratio of its thickness to the total optical path of the collimation system is 1:5 to 1:10.

[0025] Furthermore, the window protection sheet is made of fused silica, with a thickness of 0.5mm to 1.5mm, and is coated with an anti-reflective film with a transmittance greater than 99%.

[0026] Furthermore, the modulation transfer function (MTF) of the collimation system is greater than 0.6 across the entire field of view at a spatial frequency of 66 lp / mm, and the distortion rate is less than 0.15%.

[0027] Furthermore: the total length of the system is less than 50mm, and it is suitable for use in the optical waveguide display module of augmented reality (AR) glasses, with the operating wavelength range being the visible light range (400nm to 700nm).

[0028] Furthermore, the system is integrated into the waveguide display module of augmented reality (AR) glasses to collimate and couple the emitted light from the micro projection light source to the waveguide emission end, and transmit it to the human eye for imaging via the waveguide.

[0029] Furthermore, the system is applied to a vehicle head-up display (HUD) device, which projects driving information onto a designated area of ​​the windshield through the coupling of collimated light and optical waveguides to form a virtual image.

[0030] Furthermore, the system is embedded in the backlight module of a flat panel display device, and uses optical waveguide technology to achieve uniform surface light source output, thereby improving display brightness and energy efficiency.

[0031] Beneficial effects: Compared with the prior art, the compact waveguide collimation system of the present invention can meet the requirement of high-quality collimated light output when the waveguide system collimates the light. At the same time, combined with the actual optical and mechanical lens installation constraints, it achieves a compact design. While meeting the hardware size requirements, it uses spherical mirrors throughout, which effectively reduces the lens cost. In addition, the compact design simplifies the optical components of the system and reduces the optical volume of the system.

[0032] The collimation system uses spherical lenses, and by adjusting the optical power, surface shape, and relative position of each lens, high collimation performance is achieved, making it suitable for waveguide display systems. It features high collimation, high relative illumination, low distortion, good optical performance consistency, compact structure, and low cost. Attached Figure Description

[0033] Figure 1 This invention provides a schematic diagram of the optical structure of a collimation system for a compact waveguide.

[0034] Figure 2 This invention provides a modulation transfer function (MTF) curve for a collimated system for a compact waveguide.

[0035] Figure 3 This invention provides a relative illumination curve for a collimation system used in compact waveguides.

[0036] Figure 4 This invention provides a grid distortion diagram for a compact waveguide collimation system.

[0037] Figure 5 This invention provides a schematic diagram of the optical path for a compact waveguide collimation system.

[0038] Among them, 11-first lens, 12-second lens, 13-third lens, 14-fourth lens, 21-fifth lens, 22-sixth lens, 23-seventh lens, 24-eighth lens, 3-prism equivalent lens, 4-window protection sheet, 5-image plane position. Detailed Implementation

[0039] The invention will now be further explained with reference to the accompanying drawings.

[0040] The compact waveguide collimation system of this invention achieves high-quality collimated light output while realizing a compact design, effectively reducing lens costs. It can be used as a collimation element in optical waveguide display systems and can ultimately be used in fields such as smart glasses, flat panel displays, and automotive head-up displays.

[0041] Example 1

[0042] like Figure 1 The collimation system shown includes, along the optical axis from the object side to the image side, a first lens group G1, an aperture stop, a second lens group G2, a prism equivalent lens 3, a window protective plate 4, and an image plane position 5. The first lens group G1 comprises a cemented lens consisting of a first lens 11 with positive optical power, a second lens 12 with positive optical power, a third lens 13 with negative optical power, and a fourth lens 14 with negative optical power. The second lens group G2 comprises a fifth lens 21 with negative optical power, a sixth lens 22 with positive optical power, a seventh lens 23 with positive optical power, and an eighth lens 24 with positive optical power. All lenses in the collimation system are spherical mirrors, and their lens materials are all composed of glass. By adjusting the optical power, surface shape, and relative position of each lens, high collimation performance is achieved, and the object-side rays of the collimation system are incident with parallel light characteristics. The collimated rays are then focused onto the image plane position 5, making it suitable for waveguide display systems.

[0043] Example 2

[0044] Based on Example 1, the equivalent focal length of the projection lens of the collimation system, the focal length of the first lens group G1, and the focal length of the second lens group G2 satisfy the following relationship:

[0045] 1.5 < |F1 / F0| < 2.5;

[0046] 1.5 < |F2 / F0| < 2.5;

[0047] Wherein, F0 represents the equivalent focal length of the projection lens, F1 represents the focal length of the first lens group, and F2 represents the focal length of the second lens group.

[0048] Example 3

[0049] Based on Example 1, the working distance of the collimation system and the equivalent focal length of the projection lens satisfy the following relationship:

[0050] |BFL / F0|>3;

[0051] Wherein, F0 represents the equivalent focal length of the projection lens, and BFL represents the back working distance of the projection lens.

[0052] In this invention, the first lens 11 and the second lens 12 are both meniscus lenses with positive optical power, initially altering the light angle. The double-layered meniscus lens can more effectively correct aberrations. The third and fourth lenses, each with negative optical power, form a cemented lens, which can correct chromatic aberration. The third lens 13 is a biconcave lens, and the fourth lens 14 is a biconvex lens. The fifth lens 21 is a biconcave lens with negative optical power, expanding the beam of direct light and increasing the system's focal length to meet the optical-mechanical length requirements. The sixth lens 22, the seventh lens 23, and the eighth lens 24 are all biconvex lenses with positive optical power. These three lenses together form a symmetrical structure, reducing the difficulty of aberration correction in the system.

[0053] In this invention, the optical parameters of each lens are shown in the table below:

[0054]

[0055] In this invention, reference is made to Figure 1 The order of light rays in the collimation system from left to right is: 11-first lens, 12-second lens, 13-third lens, 14-fourth lens, 21-fifth lens, 22-sixth lens, 23-seventh lens, 24-eighth lens, 3-prism equivalent lens, 4-window protective plate, 5-image plane position for imaging.

[0056] In this invention, reference is made to Figure 2 The modulation transfer function of the collimation system, at a cutoff frequency of 66 lp / mm, has an MTF value higher than 0.6 under different fields of view. The MTF curve is uniform and decreases slowly, indicating that a high-quality collimation effect can be achieved.

[0057] In this invention, reference is made to Figure 3 The relative illumination curve of the collimation system shows that the relative illumination under different fields of view is greater than 0.95, indicating that the relative illumination is high, the brightness difference between the imaging center and the edge is small, and the brightness distribution is uniform.

[0058] In this invention, reference is made to Figure 4 The grid distortion of the collimation system is controlled within 0.15%, which can effectively control distortion and improve imaging quality.

[0059] The compact waveguide collimation system of this invention can achieve high-quality collimated light output. Simultaneously, considering the limitations of actual optical-mechanical lens installation, it achieves a compact design. While meeting hardware size requirements, it uses spherical mirrors throughout, effectively reducing lens costs, and employs glass materials throughout, achieving temperature stability. Furthermore, the compact design simplifies the system's optical components and reduces the system's optical volume.

[0060] Example 4

[0061] In this embodiment, a compact waveguide collimation system is integrated into the optical waveguide display module of augmented reality (AR) glasses. Light emitted from a miniature projection light source (such as a miniature LED or laser diode) is collimated by the collimation system to form highly collimated parallel light, which is then coupled into the optical waveguide sheet via an input coupling grating. The optical waveguide sheet is made of high-refractive-index glass (refractive index ≥ 1.8), and light is transmitted internally via total internal reflection, ultimately being guided to the imaging area of ​​the human eye by an output coupling grating.

[0062] Optical path details: The image plane position 5 of the collimation system is aligned with the ingress coupling grating of the optical waveguide to ensure that the diameter of the focused spot is less than 10 micrometers, thereby improving the coupling efficiency.

[0063] Adaptive design: The total system length is less than 50mm, which meets the lightweight requirements of AR glasses; the working wavelength covers the visible light range (400nm to 700nm) to match the requirements of RGB three-color light sources.

[0064] Example 5

[0065] In this embodiment, the collimation system is applied to the optical waveguide module of an in-vehicle HUD. Driving information is generated by an image generation unit (such as a DLP projection chip), converted into parallel light by the collimation system, and then coupled to a designated area of ​​the windshield through an optical waveguide sheet.

[0066] Projection logic: The output coupling grating of the optical waveguide is designed at an angle so that light is reflected by the windshield to form a virtual image. The virtual image is 2-5 meters away from the driver and is located in front of his line of sight.

[0067] Anti-interference optimization: The surface of the window protection film 4 is coated with an anti-reflection film (transmittance > 99%) to reduce ambient light interference reflected from the windshield surface; the aperture position is optimized to suppress stray light and ensure virtual image contrast.

[0068] Example 6

[0069] In this embodiment, the collimation system is embedded in the backlight module of the flat panel display device. After being collimated by the collimation system, the LED array light source is uniformly diffused into a surface light source through the optical waveguide sheet (surface etched microstructure).

[0070] Uniformity design: The microstructure density of the optical waveguide increases gradually from the center to the edge. Combined with the high relative illumination (>0.95) of the collimation system, the backlight uniformity deviation is less than 5%.

[0071] Energy efficiency improvement: The system uses low-refractive-index optical glass (refractive index 1.45-1.60) to reduce light absorption loss and improve the overall light utilization rate to over 85%.

Claims

1. A collimation system for a compact waveguide, characterized in that: The system consists of a first lens group, an aperture, a second lens group, a prism equivalent lens, a window protective sheet, and an image plane position, arranged sequentially from the object side to the image side along the optical axis. The first lens group consists of a first lens, a second lens, a third lens, and a fourth lens; wherein, The first lens is a meniscus lens with positive optical power; The second lens is a meniscus lens with positive optical power; The third lens is a biconcave lens with negative optical power, which together with the fourth lens forms a cemented lens; The fourth lens is a biconvex lens with positive optical power; The second lens group consists of a fifth lens, a sixth lens, a seventh lens, and an eighth lens; wherein, The fifth lens is a biconcave lens with negative optical power; The sixth lens is a meniscus lens with positive optical power; The seventh lens is a biconvex lens with positive optical power; The eighth lens is a biconvex lens with positive optical power; The equivalent focal length of the collimation system, the focal length of the first lens group, and the focal length of the second lens group satisfy the following relationship: 1.5 < |F1 / F0| < 2.5; 1.5 < |F2 / F0| < 2.5; F0, F1, and F2 represent the equivalent focal length of the collimation system, the focal length of the first lens group, and the focal length of the second lens group, respectively.

2. The collimation system for compact waveguides according to claim 1, characterized in that: All lenses in the first and second lens groups are spherical mirrors.

3. The collimation system for compact waveguides according to claim 1, characterized in that: The lens materials in the lens group are all optical glass, with a refractive index ranging from 1.45 to 1.85 and an Abbe number ranging from 20 to 80.

4. The collimation system for compact waveguides according to claim 1, characterized in that: The object-side rays are incident as parallel rays and focused by the collimation system onto the image plane, with the diameter of the focused spot at the image plane being less than 10 micrometers.

5. The waveguide collimation system according to claim 1, characterized in that: The back working distance and equivalent focal length of the collimation system satisfy the following relationship: |BFL / F0|>3, where BFL represents the back working distance.

6. The collimation system for compact waveguides according to claim 1, characterized in that: The modulation transfer function of the collimation system is greater than 0.6 across the entire field of view at a spatial frequency of 66 lp / mm, and the distortion rate is less than 0.15%.

7. An augmented reality glasses, characterized in that: Its optical waveguide display module integrates the compact waveguide collimation system described in any one of claims 1-6, which is used to collimate the emitted light of the micro projection light source and couple it to the waveguide emission end, and transmit it to the human eye for imaging through the waveguide.

8. A vehicle-mounted head-up display device, characterized in that: The compact waveguide collimation system according to any one of claims 1-6 projects driving information onto a designated area of ​​the windshield through the coupling of collimated light with the optical waveguide, forming a virtual image.

9. A flat panel display device, characterized in that: Its backlight module integrates the compact waveguide collimation system described in any one of claims 1-6, which realizes uniform surface light source output through optical waveguide technology, thereby improving display brightness and energy efficiency.

Images