Compact waveguide collimation system and application thereof

Abstract

The invention discloses a compact waveguide collimation system and application thereof. The compact waveguide collimation system sequentially comprises a first lens group, a diaphragm, a second lens group, a prism equivalent lens, a window protection sheet and an image plane position along an optical axis. The first lens group is combined with the bonding lens through the double-layer positive-focal-power meniscus lens, so that aberration and chromatic aberration are effectively corrected; and the second lens group adopts a negative-focal-power biconcave lens for beam expansion and is combined with a symmetrical-structure lens, so that the aberration correction difficulty is reduced. The system completely adopts spherical mirrors and glass materials, realizes the characteristics of high collimation, high relative illumination, low distortion, compact structure and low cost by optimizing the focal power, the surface type and the relative position, and is suitable for an optical waveguide display system.

Description

Technical Field

[0001] The invention relates to a compact waveguide collimation system and application thereof, and is mainly applied to collimation elements in optical waveguide displays. Background Art

[0002] Optical waveguide technology uses a dielectric substrate to make light input under certain conditions produce total reflection inside the waveguide, and uses specific optical elements to control the direction and intensity of the light, ultimately presenting the image at the display position. Due to its excellent display effect and performance characteristics, optical waveguide technology is expected to be applied to AR glasses, head-up displays, tablet computers and other fields in the future.

[0003] Optical waveguide technology can be divided into geometric waveguide and diffraction waveguide technology, which requires the in-coupling grating to input parallel light of a certain angle, which is modulated by the in-coupling grating and then totally reflected inside the waveguide to transmit the light, and finally the out-coupling grating exit pupil realizes the imaging effect. The key factor of the imaging quality of the waveguide system lies in the imaging quality of the collimation system. Therefore, the design of the collimation system is crucial in the optical waveguide display system. At the same time, the design of the collimation system also needs to comprehensively consider the type of optical machine, the size of the optical waveguide coupling, the waveguide display field of view, etc. It is expected that the ideal collimation system has a compact structure and good cost control. Therefore, designing a collimating lens with a compact structure, controllable cost and high imaging quality is one of the key and difficult points of optical design in this field. Summary of the invention

[0004] Purpose of the invention: In view of the above existing background, a compact waveguide collimation system is proposed, which can be used to generate collimated light in a waveguide system. Under the premise of meeting high imaging quality, the lens cost is effectively reduced. At the same time, the compact design simplifies the system optical components and reduces the system optical volume.

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

[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 double concave lens with negative power, and forms a cemented lens with the fourth 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 power;

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

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

[0016] Further: all lenses in the first lens group and the second lens group are spherical lenses.

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

[0018] Furthermore: the object light is incident as parallel light and is focused at the image plane position by the collimation system, and the focus spot diameter at the image plane position is less than 10 microns.

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

[0023] |BFL / F0|>3.

[0024] Furthermore: the incident surface and the exit surface of the prism equivalent lens are both planes, 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 quartz, has a thickness of 0.5 mm to 1.5 mm, and is coated with an anti-reflection film on the surface, with a transmittance greater than 99%.

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

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

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

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

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

[0031] Beneficial effect: Compared with the prior art, the compact waveguide collimation system of the present invention can meet the high-quality collimated light output when the waveguide system generates collimated light. At the same time, combined with the actual optical machine lens installation restrictions, a compact design is achieved. While meeting the hardware size, spherical mirrors are used throughout, which effectively reduces the lens cost. At the same time, the compact design simplifies the system optical components and reduces the system optical volume.

[0032] The lenses in the collimation system are all spherical mirrors. By adjusting the focal length, surface shape and relative position of each lens, high collimation of light output can be achieved, which is suitable for optical waveguide display systems. It has the characteristics of high collimation, high relative illumination, low distortion, good consistency of optical performance, compact structure and low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 A schematic diagram of the optical structure of a collimation system for a compact waveguide is created for the present invention;

[0034] Figure 2 A modulation transfer function (MTF) graph of a collimation system for a compact waveguide created for the present invention;

[0035] Figure 3 A relative illumination graph of a collimation system for a compact waveguide is created for the present invention;

[0036] Figure 4 A grid distortion diagram for a collimation system for a compact waveguide created for the present invention;

[0037] Figure 5 A schematic diagram of the optical path of a collimation system for a compact waveguide is created for the present invention.

[0038] Among them, 11 is the first lens, 12 is the second lens, 13 is the third lens, 14 is the fourth lens, 21 is the fifth lens, 22 is the sixth lens, 23 is the seventh lens, 24 is the eighth lens, 3 is the prism equivalent lens, 4 is the window protection plate, and 5 is the image plane position. DETAILED DESCRIPTION

[0039] The present invention will be further explained below in conjunction with the accompanying drawings.

[0040] The compact waveguide collimation system in the present invention is designed to meet the requirements of high-quality collimated light output while achieving a compact design, effectively reducing lens costs, and can be used as a collimation element for optical waveguide display systems, and can ultimately be used in the fields of smart glasses, flat panel displays, and vehicle-mounted head-up displays.

[0041] Example 1

[0042] like Figure 1 The collimation system shown includes a first lens group G1, an aperture, a second lens group G2, a prism equivalent lens 3, a window protection sheet 4 and an image plane position 5 along the optical axis from the object side to the image side; the first lens group G1 includes a first lens 11 with positive focal power, a second lens 12 with positive focal power, a third lens 13 with negative focal power and a fourth lens 14 with negative focal power. The second lens group G2 includes a fifth lens 21 with negative focal power, a sixth lens 22 with positive focal power, a seventh lens 23 with positive focal power, and an eighth lens 24 with positive focal power. The lenses in the collimation system are all spherical mirrors, and their lens materials are all made of glass materials. By adjusting the focal power, surface shape and relative position of each lens, a high collimation light output performance is achieved, and the object side light of the collimation system is incident with parallel light characteristics. And it is focused on the image plane position 5 through the collimation system, which is suitable for optical waveguide display systems.

[0043] Example 2

[0044] Based on Example 1, the equivalent focal length of the projection lens of the collimating 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 rear 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 the present invention, the first lens 11 is a meniscus lens with positive focal power, and the second lens 12 is a meniscus lens with positive focal power, which preliminarily changes the angle of the light. The double-layer meniscus lens can correct aberrations more effectively. The third lens with negative focal power and the fourth lens with negative focal 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 focal power, which expands the collimated light and expands the focal length of the system to meet the optical machine size length requirements. The sixth lens 22 is a meniscus lens with positive focal power, the seventh lens 23 is a biconvex lens with positive focal power, and the eighth lens 24 is a biconvex lens with positive focal power. The three lenses together form a symmetrical structure, which reduces the difficulty of correcting aberrations in the system.

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

[0054]

[0055] In the present 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 protection sheet, 5-image plane position for imaging.

[0056] In the present invention, reference is made to Figure 2 : Modulation transfer function of the collimation system. When the cutoff frequency is 66lp / mm, the MTF values ​​under different fields of view are all higher than 0.6. The MTF curve is uniform and decreases slowly, indicating that high-quality collimation effect can be achieved.

[0057] In the present 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 the present invention, reference is made to Figure 4 :The grid distortion of the collimation system is controlled within 0.15%, which can effectively control the distortion and improve the imaging quality.

[0059] The compact waveguide collimation system of the present invention can meet the requirements of high-quality collimated light output. At the same time, it realizes a compact design by combining the installation restrictions of the actual optical machine lens. Under the condition of meeting the hardware size, all spherical mirrors are used, which effectively reduces the lens cost. All glass materials are used to achieve temperature stability. At the same time, the compact design simplifies the system optical components and reduces the system optical volume.

[0060] Example 4

[0061] In this embodiment, the compact waveguide collimation system is integrated into the optical waveguide display module of augmented reality (AR) glasses. The light emitted by the micro-projection light source (such as micro-LED or laser diode) forms highly collimated parallel light after passing through the collimation system, and is coupled to the inside of the optical waveguide sheet through the in-coupling grating. The optical waveguide sheet is made of high-refractive index glass material (refractive index ≥ 1.8), and the light is transmitted internally by total reflection, and finally guided to the imaging area of ​​the human eye by the out-coupling grating.

[0062] Optical path details: The image plane position 5 of the collimation system is aligned with the in-coupling grating of the optical waveguide to ensure that the focused spot diameter is less than 10 microns to improve the coupling efficiency.

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

[0064] Example 5

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

[0066] Projection logic: The outcoupling grating of the optical waveguide is designed to be tilted so that the light forms a virtual image after being reflected by the windshield. The virtual image is 2-5 meters away from the driver and is located in front of the line of sight.

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

[0068] Example 6

[0069] The collimation system described in this embodiment 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 evenly 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] Improved energy efficiency: The system uses low-refractive-index optical glass (refractive index 1.45-1.60) to reduce light absorption loss and increase overall light utilization to more than 85%.

Claims

1. A compact waveguide collimation system, characterized in that: The system includes a first lens group, an aperture, a second lens group, a prism equivalent lens, a window protection sheet and an image plane position in sequence from the object side to the image side along the optical axis; The first lens group includes 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 double concave lens with negative power, and forms a cemented lens with the fourth lens; The fourth lens is a biconvex lens with negative optical power; The second lens group includes 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 power; The seventh lens is a biconvex lens with positive power; The eighth lens is a biconvex lens with positive refractive power.

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

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

4. The compact waveguide collimation system according to claim 1, characterized in that: The object light is incident as parallel light and is focused on the image plane by the collimation system, and the focus spot diameter at the image plane is less than 10 microns.

5. The waveguide collimation system according to claim 1, characterized in that: 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: 1.5<|F1 / F0|<2.5; 1.5<|F2 / F0|<2.

5.

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

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

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

9. A vehicle head-up display (HUD) device, characterized in that: The collimation system for a compact waveguide comprises any one of claims 1 to 6, and the driving information is projected onto a designated area of ​​a windshield to form a virtual image by coupling the collimated light with the optical waveguide.

10. A flat panel display device, characterized in that: The backlight module thereof integrates the compact waveguide collimation system described in any one of claims 1 to 6, realizes uniform surface light source output through optical waveguide technology, and improves display brightness and energy efficiency.

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