Virtual exit pupil micro-projection lens

Abstract

The application discloses a virtual exit pupil micro-projection lens, which comprises a virtual diaphragm, a first lens, a second lens, a third lens, a fourth lens and an image source plane which are sequentially and separately arranged along the same optical axis from the imaging side to the image source side, wherein the first lens and the third lens both have positive focal power; the second lens and the fourth lens both have negative focal power; the effective focal length of the projection lens is EFL, the distance between the surface center point of the imaging side of the first lens and the image source plane is TTL, the distance between the virtual exit pupil center of the projection lens and the surface center point of the imaging side of the first lens is ENPP, and the virtual exit pupil diameter of the projection lens is ENPD, which satisfy the following relationship: the volume of the projection lens is small, the near-eye display effect is good, the use scene of the wearable device can be better adapted, and the use value of the product is improved.

Description

Technical Field

[0001] This invention relates to the field of optical lens technology, and in particular to a virtual exit pupil miniature projection lens. Background Technology

[0002] Augmented Reality (AR) technology is a technique that cleverly integrates virtual information with the real world. It widely utilizes multimedia, 3D modeling, real-time tracking and registration, intelligent interaction, and sensing technologies to simulate computer-generated text, images, 3D models, music, videos, and other virtual information. This simulation is then displayed near the eye using a micro-projector, thus "enhancing" the real world. With the continuous development of AR technology, lightweight design and ultra-high definition are the research trends for AR devices. Current micro-projectors use a combination of projection lenses and Micro LEDs to improve display quality.

[0003] In the current technology, the single green micro-projection light engine paired with a Micro LED display screen is currently the mainstream optical engine for AR display diffraction waveguides. The micro-projection light engine collimates the Micro LED display image into freely focusable parallel light, which is projected through the exit pupil of the optical engine onto the coupling grating position of the diffraction waveguide. The coupling grating of the diffraction waveguide couples the projected image light into the waveguide for transmission and pupil expansion replication. Finally, the diffraction waveguide output grating couples the pupil-expanded and replicated projected image light out, which is then incident on the human eye for normal imaging, realizing the AR display function.

[0004] However, current combinations of projection lenses and Micro LEDs typically place the aperture stop within the front structure of the projection lens. This results in a significant increase in the aperture of the light spot transmitted through the aperture stop, requiring an increase in the diameter of the coupling grating. Consequently, light may re-enter the coupling grating, causing additional energy loss, reducing the uniformity of the waveguide display, and affecting the display effect. Furthermore, the micro projector is relatively large, making the size and weight of the head-mounted device significantly different from conventional glasses, thus affecting wearing comfort.

[0005] Therefore, existing technologies still need to be improved and developed. Summary of the Invention

[0006] In view of the shortcomings of the prior art, the purpose of this invention is to provide a virtual exit pupil micro-projection lens, which aims to solve the problems of large size and poor display effect of the combination of projection lens and Micro LED used in existing head-mounted augmented reality devices.

[0007] The technical solution of the present invention is as follows:

[0008] A virtual exit pupil miniature projection lens includes a virtual aperture, a first lens, a second lens, a third lens, a fourth lens, and an image source surface, which are sequentially spaced along the same optical axis from the imaging side to the image source side. The first lens and the third lens both have positive optical power; the second lens and the fourth lens both have negative optical power.

[0009] The effective focal length of the projection lens is EFL, the distance between the center point of the imaging side surface of the first lens and the image source surface is TTL, the distance between the virtual exit pupil center of the projection lens and the center point of the imaging side surface of the first lens is ENPP, and the virtual exit pupil diameter of the projection lens is ENPD, satisfying the following relationship:

[0010]

[0011]

[0012]

[0013] The virtual exit pupil micro-projection lens, wherein the fourth lens has at least one inflection point on the image source side.

[0014] The virtual exit pupil micro-projection lens includes a screen protection lens, which is disposed between the fourth lens and the image source surface along the same optical axis.

[0015] The virtual exit pupil micro-projection lens, wherein the first lens is a glass lens; the second lens, the third lens and the fourth lens are all plastic lenses.

[0016] The virtual exit pupil miniature projection lens, wherein the first lens has a refractive index of n1 and an Abbe number of VD1; the second lens has a refractive index of n2 and an Abbe number of VD2; the third lens has a refractive index of n3 and an Abbe number of VD3; and the fourth lens has a refractive index of n4 and an Abbe number of VD4; satisfying the following relationship:

[0017] 1.59≤n1≤1.64, 55≤VD1≤66;

[0018] 1.61≤n2≤1.68,19≤VD2≤26;

[0019] 1.61≤n3≤1.68, 24≤VD3≤30;

[0020] 1.61≤n4≤1.68,19≤VD4≤26。

[0021] The virtual exit pupil micro-projection lens, wherein the optical power of the projection lens is... The optical power of the first lens is The optical power of the second lens is The optical power of the third lens is The following relationship must be satisfied:

[0022]

[0023]

[0024] The virtual exit pupil miniature projection lens, wherein the distance from the center point of the image source side of the first lens to the center point of the imaging side of the second lens is CT. 12 The distance from the center point of the image source side of the third lens to the center point of the image side of the fourth lens is CT. 34 It satisfies the following relationship:

[0025]

[0026] The virtual exit pupil miniature projection lens, wherein half of the field of view along the diagonal direction of the projection lens is H. FOv The distance between the center point of the image source side surface of the fourth lens and the image source surface is BFL, which satisfies the following relationship:

[0027] 13°≤H FOV ≤16°;

[0028]

[0029] The virtual exit pupil micro-projection lens, wherein the curvature of the center point of the surface on the imaging side of the first lens is C. 11 The curvature of the center point of the surface on the image source side of the first lens is C. 12 It satisfies the following relation:

[0030]

[0031] The virtual exit pupil micro-projection lens, wherein the curvature of the center point of the surface on the imaging side of the second lens is c. 21 The curvature of the center point of the surface on the image source side of the second lens is c. 22 The curvature of the center point of the surface on the imaging side of the third lens is c. 31 The curvature of the center point of the surface on the image source side of the third lens is c. 32 The following relationship must be satisfied:

[0032] C 21 ≥0, C22 ≥0;

[0033] C 31 ≤0, C 32 ≤0.

[0034] Compared with the prior art, the embodiments of the present invention have the following advantages:

[0035] The virtual exit pupil micro-projection lens disclosed in this invention separates the virtual aperture from the micro-projector and places it on the imaging side of the first lens, so that the virtual aperture is located at the front end of the micro-projector, forming a virtual exit pupil. This reduces the distance between the virtual exit pupil and the waveguide coupling grating, thereby reducing the diffusion of the light spot emitted from the first lens, which is beneficial for improving the uniformity of the optical waveguide display and enhancing the display effect. Four lenses are arranged between the virtual aperture and the image source surface. The first and third lenses have positive optical power, while the second and fourth lenses have negative optical power. This design results in a projection lens with a small overall optical length, a large aperture, and high light efficiency, capable of projecting brighter and better-looking images at rated power consumption. In summary, the virtual exit pupil micro-projection lens disclosed in this embodiment reduces size and enhances near-eye display effects, facilitating its combination with Micro LED to manufacture lightweight, ultra-high-definition head-mounted augmented reality devices. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 This is a schematic diagram of the structure of the virtual exit pupil micro-projection lens in this invention;

[0038] Figure 2 This is a schematic diagram of the optical path of the virtual exit pupil micro-projection lens in this invention;

[0039] Figure 3 This is a modulation transfer function curve of a virtual exit pupil micro-projection lens in one embodiment of the present invention;

[0040] Figure 4 This is a field curvature curve and distortion curve diagram of a virtual exit pupil micro-projection lens in one embodiment of the present invention;

[0041] Figure 5 This is an axial chromatic aberration curve of a virtual exit pupil micro-projection lens in one embodiment of the present invention;

[0042] Figure 6This is a chromatic aberration curve of the virtual exit pupil micro-projection lens in one embodiment of the present invention;

[0043] Figure 7 This is a relative illumination curve of a virtual exit pupil micro-projection lens in one embodiment of the present invention;

[0044] Figure 8 This is an MTF curve of a virtual exit pupil micro-projection lens in a -10℃ environment according to an embodiment of the present invention;

[0045] Figure 9 This is an MTF curve of the virtual exit pupil micro-projection lens in a 25°C environment according to an embodiment of the present invention;

[0046] Figure 10 This is an MTF curve of the virtual exit pupil micro-projection lens in a 60°C environment according to an embodiment of the present invention;

[0047] Figure 11 This is a modulation transfer function curve of the virtual exit pupil micro-projection lens in another embodiment of the present invention;

[0048] Figure 12 This is a field curvature curve and distortion curve diagram of the virtual exit pupil micro-projection lens in another embodiment of the present invention;

[0049] Figure 13 This is an axial chromatic aberration curve of the virtual exit pupil micro-projection lens in another embodiment of the present invention;

[0050] Figure 14 This is a chromatic aberration curve of the virtual exit pupil micro-projection lens in another embodiment of the present invention;

[0051] Figure 15 This is a relative illumination curve of the virtual exit pupil micro-projection lens in another embodiment of the present invention;

[0052] Figure 16 This is an MTF curve of the virtual exit pupil micro-projection lens in a -10℃ environment according to another embodiment of the present invention;

[0053] Figure 17 This is an MTF curve of the virtual exit pupil micro-projection lens in a 25°C environment according to another embodiment of the present invention;

[0054] Figure 18 This is an MTF curve of the virtual exit pupil micro-projection lens in a 60°C environment, according to another embodiment of the present invention.

[0055] Among them, 10 is the virtual aperture; 20 is the first lens; 30 is the second lens; 40 is the third lens; 50 is the fourth lens; 60 is the image source surface; and 70 is the screen protection lens. Detailed Implementation

[0056] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0057] Currently, head-mounted AR glasses have a promising market prospect and are widely favored by consumers. However, the micro-projector used in AR glasses with Micro LEDs is relatively large, generally larger than 0.5cc. When the micro-projector is placed in the temple of the AR glasses, it is not conducive to making the temple of the AR glasses smaller, which affects the shape design of the AR glasses. This makes the shape design of AR glasses significantly different from that of everyday nearsighted or farsighted glasses. Moreover, the large size of the projector also increases the weight of the glasses, affecting the user's wearing comfort and making them inconvenient for long-term wear.

[0058] Furthermore, in current Micro LED projectors, the aperture is placed within the front-end structure of the lens, close to the distance of the first lens of the projection lens. This causes the light spot diameter to enlarge after passing through the aperture. For reflective diffractive waveguides, the coupling grating is located on the side of the waveguide furthest from the eye. Light passing through the aperture needs to pass through a waveguide layer of a certain thickness before entering the coupling grating for coupling. For transmissive diffractive waveguides, although the coupling grating is closer to the eye, a protective cover is attached between the coupling grating and the projector to protect the grating layer. Light must pass through this protective cover before entering the coupling grating for coupling. Therefore, in either case, if the aperture of the projector is placed within the front-end structure of the lens, the light... After passing through the aperture of the lens, light must pass through at least the thickness of the waveguide layer or protective cover before it can be coupled to the coupling grating. This results in a significant increase in the spot diameter. The diameter of the coupling grating needs to be increased accordingly to receive all the light emitted from the aperture of the micro projector and couple it for pupil expansion display. In actual manufacturing, if the diameter of the coupling grating is made too large, the light will not be able to leave the coupling region after the first diffraction coupling and will be incident on the coupling grating a second time for secondary diffraction, resulting in additional energy loss and affecting the waveguide light efficiency.

[0059] In addition, the diffusion of the light spot will cause the light spots in different fields of view to gradually separate. The farther the diffusion distance, the greater the degree of separation. The separation of light spots in different fields of view will affect the uniformity of the optical waveguide display, resulting in poor display effect.

[0060] See Figure 1 and Figure 2In one embodiment of this invention application, a virtual exit pupil micro-projection lens is disclosed, comprising a virtual aperture 10, a first lens 20, a second lens 30, a third lens 40, a fourth lens 50, and an image source surface 60, arranged sequentially along the same optical axis from the imaging side to the image source side. The first lens 20 and the third lens 40 both have positive optical power; the second lens 30 and the fourth lens 50 both have negative optical power; the effective focal length of the projection lens is EFL; the distance between the center point of the imaging side surface of the first lens 20 and the image source surface 60 is TTL; the distance between the center of the virtual exit pupil of the projection lens and the center point of the imaging side surface of the first lens 20 is ENPP; and the virtual exit pupil diameter of the projection lens is ENPD, satisfying the following relationship:

[0061]

[0062]

[0063]

[0064] The virtual exit pupil micro-projection lens disclosed in this embodiment separates the virtual aperture stop 10 from the micro-projector and places it on the imaging side of the first lens 20. The term "virtual exit pupil" refers to the aperture stop not using the physical structure of the lens to limit the aperture of the projected beam, but rather placing the aperture stop at a specific distance in front of the micro-projector and constraining it through the entrance pupil size of the next optical system. For example, the entrance pupil diameter can be used in conjunction with the coupling grating of a diffractive waveguide to systematically achieve the effect of constraining the beam's aperture.

[0065] In this embodiment, the projection lens places the virtual aperture 10 in front, increasing the distance between the virtual aperture 10 and the first lens 20. This separates the aperture of the micro-projector from the micro-projector structure itself, forming a virtual exit pupil at a virtual position. Since the virtual exit pupil is farther from the front end structure of the optical engine, the light emitted from the micro-projector will converge at the front end of the micro-projector, reducing the distance between the micro-projector exit pupil and the waveguide coupling grating. This greatly mitigates the adverse effects of light spot diffusion, enhances the light efficiency of the optical waveguide display, increases the uniformity of the optical waveguide display, and improves the AR display effect.

[0066] Specifically, four lenses are arranged between the virtual aperture 10 and the image source surface 60. The first lens 20 and the third lens 40 both have positive optical power, while the second lens 30 and the fourth lens 50 both have negative optical power. The projection lens is designed with a small total optical length, a large light-passing aperture, and high light efficiency, which can project a brighter and better-looking projection image under rated power consumption.

[0067] Specifically, the virtual exit pupil micro-projection lens proposed in this embodiment is small in size and can be paired with a commercially available 0.13-inch Micro LED display to reduce the size of the micro-projector to 0.3CC, thus further reducing the temple size of the AR glasses. Furthermore, due to the reduction in the overall length of the projection lens, the hinge of the temple can be designed closer to the waveguide plate, which helps to make the AR glasses more similar to ordinary eyeglasses worn daily, better meeting ergonomic requirements, improving wearing comfort, and facilitating prolonged wear. The virtual exit pupil micro-projection lens proposed in this embodiment... A larger value indicates a smaller relative total optical length of the projection lens, which is beneficial for miniaturizing the projection optical engine. This value should be set in conjunction with actual manufacturing process parameters. Values ​​in the range of 0.89 to 0.94 allow for the manufacture of small projection lenses suitable for use in AR glasses.

[0068] The embodiments disclosed herein A value greater than 0.11 is beneficial for increasing the distance between the virtual exit pupil and the first lens 20. A ratio in the range of 0.11-0.19 is beneficial for separating the aperture of the micro-projector from the optomechanical structure itself. Setting the virtual aperture 10 at the front end of the micro-projector forms a virtual exit pupil at a virtual position, reducing the distance between the virtual exit pupil and the waveguide coupling grating in the micro-projector, greatly mitigating the adverse effects of light spot diffusion, and benefiting the design of the light efficiency and uniformity of the waveguide display.

[0069] The embodiments disclosed herein The smaller the value, the larger the aperture of the projection lens, the higher the light efficiency, and the brighter the projected image under rated power consumption. A value in the range of 1.60-1.85 can meet the input optical flux requirements of most diffractive waveguides for micro-projectors.

[0070] In summary, the virtual exit pupil micro-projection lens disclosed in this embodiment reduces the size and enhances the near-eye display effect, which is beneficial for combining the virtual exit pupil micro-projection lens with Micro LED to manufacture lightweight, ultra-high-definition head-mounted augmented reality devices.

[0071] like Figure 1 and Figure 2As shown in this embodiment, the fourth lens 50 has at least one inflection point on the image source side. The first lens 20, second lens 30, third lens 40, and fourth lens 50 disclosed in this embodiment are all aspherical lenses. Furthermore, at least one inflection point is provided on the image source side of the fourth lens 50. An inflection point refers to a point where the sign of curvature changes. This helps to fully optimize the shape of each lens, thereby reducing the lens size and decreasing the sensitivity of keyboard assembly. This facilitates the assembly of a projection lens with more precise dimensions, improves the resolution performance of the projection lens, and projects a clearer image.

[0072] For example Figure 1 As shown, in another embodiment of this invention, the virtual exit pupil micro-projection lens includes a screen protection lens 70, which is disposed between the fourth lens 50 and the image source surface 60 along the same optical axis. In this embodiment, the screen protection lens 70 is disposed on the image source side of the fourth lens 50. The screen protection lens 70 can be made of glass or plastic material and is a planar lens with both sides being flat. Specifically, the screen protection lens 70 itself is a protective lens for the light emission exit of the image source, mainly to protect the light emission structure of the image source and prevent external dust from entering the light emission structure of the image source to avoid contamination and affect image quality.

[0073] Specifically, as another embodiment of this invention, the first lens 20 is disclosed as a glass lens; the second lens 30, the third lens 40, and the fourth lens 50 are all plastic lenses. Since the coefficient of thermal expansion and the refractive index of a glass lens are significantly smaller than those of a plastic lens relative to temperature, concentrating the optical power of the projection lens primarily in the first lens 20 helps to make the projection lens less sensitive to temperature, thereby achieving a heat-free design.

[0074] Specifically, in this embodiment, the second lens 30, the third lens 40, and the fourth lens 50 of the projection lens are all made of plastic. Because plastic lenses have a large coefficient of thermal expansion and their refractive index changes more significantly with temperature.

[0075] Specifically, in this embodiment, in order to achieve the overall heatless design of the projection lens, the temperature drift of the plastic lens with positive optical power and the plastic lens with negative optical power needs to cancel each other out. Therefore, the first lens 20 and the third lens 40 are both set to have positive optical power; the second lens 30 and the fourth lens 50 are both set to have negative optical power. That is, the lenses with positive and negative optical power are set alternately, so that the focus drift caused by temperature of the positive and negative lenses can cancel each other out, thereby achieving the heatless design effect.

[0076] Specifically, as another embodiment of this invention, the refractive index of the first lens 20 is disclosed as n1, and the Abbe number of the first lens 20 is VD1; the refractive index of the second lens 30 is n2, and the Abbe number of the second lens 30 is VD2; the refractive index of the third lens 40 is n3, and the Abbe number of the third lens 40 is VD3; the refractive index of the fourth lens 50 is n4, and the Abbe number of the fourth lens 50 is VD4; satisfying the following relationship:

[0077] 1.59≤n1≤1.64, 55≤VD1≤66;

[0078] 1.61≤n2≤1.68,19≤VD2≤26;

[0079] 1.61≤n3≤1.68, 24≤VD3≤30;

[0080] 1.61≤n4≤1.68,19≤VD4≤26。

[0081] In this embodiment, when the refractive index and Abbe number of the first lens 20 meet the above-mentioned range, it is advantageous for the first lens 20 to be made of glass. When the refractive index and Abbe number of the second lens 30, third lens 40, and fourth lens 50 meet the above-mentioned range, it is advantageous for the second lens 30, third lens 40, and fourth lens 50 to be made of plastic. Ultimately, the virtual exit pupil micro-projection lens disclosed in this embodiment adopts an architecture of one glass lens and three plastic lenses. Since plastic has a lower density than glass, this helps to reduce the weight of the lens. Furthermore, because plastic materials are easy to process and not easily broken, plastic lenses have greater design freedom than glass lenses. Using plastic lenses can further reduce the lens size while also improving optical resolution performance.

[0082] Specifically, as another implementation of this embodiment, the optical power of the projection lens is disclosed as follows: The optical power of the first lens 20 is The optical power of the second lens 30 is The optical power of the third lens 40 is The following relationship must be satisfied:

[0083]

[0084]

[0085] In this embodiment, the first lens 20 is located on the imaging side. The second lens 30, third lens 40, and fourth lens 50 are arranged sequentially along the direction closest to the image source side. The second lens 30 is the plastic lens furthest from the image source surface 60, and its contribution to the overall optical power of the lens is relatively greater. The fourth lens 50 is the plastic lens closest to the image source surface 60, and its contribution to the overall optical power of the lens is lower. During the use of the virtual exit pupil micro-projection lens, the fourth lens 50 does not contribute much to the overall temperature drift of the projection lens. Therefore, the main contribution to the temperature drift of the virtual exit pupil micro-projection lens comes from the second lens 30 and the third lens 40. The second lens 30 has a negative optical power, and the third lens 40 has a positive optical power. By adjusting the optical power of the second lens 30 to be lower than that of the third lens 40, the temperature drift can be canceled out. That is to say, the ratio of the optical power of the second lens 30 and the third lens 40 satisfies This allows for a heatless design of the projection lens, enabling the miniature projection lens to operate well over a wider temperature range.

[0086] Specifically, as another embodiment of this invention, the distance from the center point of the image source side of the first lens 20 to the center point of the imaging side of the second lens 30 is disclosed as CT. 12 The distance from the center point of the image source side of the third lens 40 to the center point of the imaging side of the fourth lens 50 is CT. 34 It satisfies the following relationship:

[0087]

[0088] The lenses disclosed in this embodiment are all aspherical lenses, but both sides are curved surfaces. Therefore, the height of the light rays at the edge of the central field of view is different when the lens is in different positions. Moreover, the temperature drift of the projection lens will also be different when the lens is in different positions. This embodiment sets... The value is in the range of 0.24 to 0.34. Meeting this condition is beneficial for maintaining a reasonable spacing between plastic lenses and between plastic lenses and glass lenses. It is also beneficial for controlling the temperature drift of the projection lens, enabling heatless design, reducing the sensitivity of lens assembly, and improving assembly yield.

[0089] Specifically, as another implementation of this embodiment, it is disclosed that half of the field of view of the projection lens along the diagonal direction is H. FOV The distance between the center point of the image source side surface of the fourth lens 50 and the image source surface 60 is BFL, which satisfies the following relationship:

[0090] 13°≤H FOV ≤16°;

[0091]

[0092] The virtual exit pupil micro-projection lens disclosed in this embodiment is small in size, with half of its field of view controlled within the range of 13° to 16°. It can be used with a commercially available 0.13-inch Micro LED display with a resolution of 640×480, allowing the final projection device to display an AR image with a relatively large field of view and high angular resolution, thus facilitating better near-eye display effects. The value is controlled within the range of 0.1-0.17, which ensures sufficient distance between the fourth lens 50 and the image source surface 60. This allows the virtual exit pupil micro-projection lens to reserve enough back focal space, facilitating screen assembly and adjustment.

[0093] Specifically, as another embodiment of this invention, the curvature of the center point of the surface on the imaging side of the first lens 20 is disclosed as C. 11 The curvature of the center point of the surface on the image source side of the first lens 20 is C. 12 It satisfies the following relation:

[0094]

[0095] The first lens 20, the second lens 30, the third lens 40, and the fourth lens 50 disclosed in this embodiment are all aspherical lenses, which is beneficial for reasonably matching the shape of the lenses, reducing the sensitivity of lens assembly, and thus improving the resolution performance of the projection virtual exit pupil micro-lens. When applied to projection devices, it can project images with higher clarity.

[0096] Specifically, as another embodiment of this invention, the curvature of the center point of the surface on the imaging side of the second lens 30 is disclosed as c. 21 The curvature of the center point of the surface on the image source side of the second lens 30 is c. 22 The curvature of the center point of the surface on the imaging side of the third lens 40 is c. 31 The curvature of the center point of the surface on the image source side of the third lens 40 is c. 32 The following relationship must be satisfied:

[0097] C 21 ≥0, C 22 ≥0;

[0098] C 31 ≤0, C 32 ≤0.

[0099] When the second lens 30 and the third lens 40 in this embodiment meet this condition, it is beneficial to reduce the size of the virtual exit pupil micro-projection lens and reduce the sensitivity of lens assembly, thereby improving the resolution performance of the virtual exit pupil micro-projection lens.

[0100] Specifically, as another embodiment of this invention, a virtual exit pupil micro-projection lens is disclosed, wherein a virtual aperture 10, a first lens 20, a second lens 30, a third lens 40, a fourth lens 50, a screen protection lens 70, and an image source surface 60 are sequentially and spaced apart along the same optical axis from the imaging side to the image source side. Table 1 shows the lens parameters of the virtual exit pupil micro-projection lens of this embodiment.

[0101] Table 1

[0102]

[0103] Table 2 shows the aspherical coefficients of each lens surface of the virtual exit pupil micro-projection lens in this embodiment. In this embodiment, each surface of the lens is an even-order aspherical surface. The definition formula for an even-order aspherical surface in ZEMAX is as follows:

[0104]

[0105] Where z is the sagitta of the lens surface under different apertures; c is the reciprocal of the radius of curvature; k is the conic coefficient; r is the aperture in the radial direction; the quadratic term in Table 2 is α1r in the formula. 2 The aspherical coefficient α1; the 4th term is α2r in the formula. 4 The aspherical coefficient α2; the 6th term is α3r in the formula. 6 The aspheric coefficient α3; the 8th term is α4r in the formula. 8 The aspheric coefficient α4; the 10th term is α5r in the formula. 10 The aspherical coefficient α5. In Table 2, the surfaces numbered 2 to 9 are, in order, the imaging side surface of the first lens 20, the image source side surface of the first lens 20, the imaging side surface of the second lens 30, the image source side surface of the second lens 30, the imaging side surface of the third lens 40, the image source side surface of the third lens 40, the imaging side surface of the fourth lens 50, and the image source side surface of the fourth lens 50.

[0106] Table 2

[0107]

[0108]

[0109] Table 3 shows the specifications of the virtual exit pupil micro-projection lens in this embodiment. Wherein, i mgh Half the diagonal length of the effective projection area of ​​the image source surface of the projector; H FOV ENPD is half the field of view angle of the projection lens along the diagonal direction, and ENPD is the virtual exit pupil diameter of the projection lens.

[0110] Table 3

[0111] <![CDATA[I mgh ]]> 1.600mm <![CDATA[H FOV ]]> 15° ENPD 3.61mm

[0112] Table 4 shows the spectral range emitted from the image source surface of the projection optical engine in this embodiment.

[0113] Table 4

[0114]

[0115] Finally, the virtual exit pupil micro-projection lens disclosed in this embodiment was tested, paired with a Micro LED display with a single pixel size of 4 micrometers.

[0116] like Figure 3 As shown, the modulation transfer function (MTF) is a method for evaluating the ability to reproduce details of a scene, and can comprehensively and objectively characterize the sharpness of an image. MTF can be used to represent the characteristics of an optical system; the larger the MTF, the better the image quality of the system. In this embodiment, the virtual exit pupil micro-projection lens, when paired with a Micro LED display with a pixel size of 4 micrometers, exhibits a modulation transfer function greater than 0.5 even at the full Nyquist frequency of 125 lp / mm, indicating that the lens has good resolving performance and can project high-definition images.

[0117] like Figure 4 As shown, the field curvature of the virtual exit pupil micro-projection lens disclosed in this embodiment is within 20 micrometers, and the optical distortion is within 1.5%, indicating that the projection lens can project a projected image that is not obviously distorted when viewed.

[0118] like Figure 5 As shown, the axial color difference of the virtual exit pupil micro-projection lens disclosed in this embodiment is within 37 micrometers, indicating that when the projection lens is paired with a Micro LED display screen with a single pixel size of 4 micrometers, there is no obvious color shift in the center of the projected image.

[0119] like Figure 6 As shown, the chromatic aberration of the virtual exit pupil micro-projection lens disclosed in this embodiment is within the diffraction limit, indicating that when the projection lens is paired with a Micro LED display with a single pixel size of 4 micrometers, there is no obvious purple or red fringing around the projected image.

[0120] like Figure 7 As shown, the virtual exit pupil micro-projection lens disclosed in this embodiment has a peripheral brightness ratio of over 88%, which can project a uniformly illuminated image.

[0121] like Figure 8 , Figure 9 and Figure 10 As shown, compared with a normal temperature environment of 25℃, the virtual exit pupil micro-projection lens disclosed in this embodiment has a back focal temperature drift of less than ±6.5 micrometers in the range of low temperature -10℃ and high temperature 60℃. Moreover, after the temperature drift, the MTF of most fields of view at the full Nyquist frequency of 125lp / mm is greater than 0.3, indicating that the virtual exit pupil micro-projection lens disclosed in this embodiment can work well even in cold and hot environments and has strong adaptability to the usage environment.

[0122] Specifically, in another embodiment of this invention, another virtual exit pupil micro-projection lens is disclosed, wherein a virtual aperture 10, a first lens 20, a second lens 30, a third lens 40, a fourth lens 50, a screen protection lens 70, and an image source surface 60 are sequentially and spaced apart along the same optical axis from the imaging side to the image source side. Table 5 shows the lens parameters of the virtual exit pupil micro-projection lens of this embodiment.

[0123] Table 5

[0124]

[0125] Table 6 shows the aspherical coefficients of each lens surface of the virtual exit pupil micro-projection lens in this embodiment.

[0126] Table 6

[0127]

[0128]

[0129] The virtual exit pupil micro-projection lens disclosed in this embodiment was tested and paired with a Micro LED display with a single pixel size of 4 micrometers.

[0130] like Figure 11 As shown, the virtual exit pupil micro-projection lens disclosed in this embodiment, when paired with a Micro LED display with a single pixel size of 4 micrometers, exhibits a modulation transfer function greater than 0.5 even at the full Nyquist frequency of 125 lp / mm, indicating that the lens has good resolution performance and can project high-definition images.

[0131] like Figure 12 As shown, the field curvature of the virtual exit pupil micro-projection lens disclosed in this embodiment is within 0.05 mm, and the optical distortion is within 1.5%, indicating that the projection lens can project a projected image that is not obviously distorted when viewed.

[0132] like Figure 13As shown, the axial color difference of the virtual exit pupil micro-projection lens disclosed in this embodiment is within 37 micrometers, indicating that when the projection lens is paired with a Micro LED display screen with a single pixel size of 4 micrometers, there is no obvious color shift in the center of the projected image.

[0133] like Figure 14 As shown, the chromatic aberration of the virtual exit pupil micro-projection lens disclosed in this embodiment is within the diffraction limit, indicating that when the projection lens is paired with a Micro LED display with a single pixel size of 4 micrometers, there is no obvious purple or red fringing around the projected image.

[0134] like Figure 15 As shown, the virtual exit pupil micro-projection lens disclosed in this embodiment has a peripheral brightness ratio of over 85%, which can project a uniformly illuminated image.

[0135] like Figure 16 , Figure 17 and Figure 18 As shown, compared with a normal temperature of 25°C, the virtual exit pupil micro-projection lens disclosed in this embodiment has a back focal temperature drift of less than ±9 micrometers in the range of low temperature -10°C and high temperature 60°C. Moreover, after the temperature drift, the MTF of most fields of view at the full Nyquist frequency of 125 lp / mm is greater than 0.3, indicating that the virtual exit pupil micro-projection lens disclosed in this embodiment can work well even in cold and hot environments and has strong adaptability to the usage environment.

[0136] In summary, this application discloses a virtual exit pupil micro-projection lens, comprising a virtual aperture 10, a first lens 20, a second lens 30, a third lens 40, a fourth lens 50, and an image source surface 60, arranged sequentially along the same optical axis from the imaging side to the image source side. The first lens 20 and the third lens 40 both have positive optical power; the second lens 30 and the fourth lens 50 both have negative optical power; the effective focal length of the projection lens is EFL; the distance between the center point of the imaging side surface of the first lens 20 and the image source surface 60 is TTL; the distance between the center of the virtual exit pupil of the projection lens and the center point of the imaging side surface of the first lens 20 is ENPP; and the virtual exit pupil diameter of the projection lens is ENPD, satisfying the following relationship:

[0137] The virtual exit pupil micro-projection lens disclosed in this embodiment separates the virtual aperture 10 from the micro-projector and positions it on the imaging side of the first lens 20, so that the virtual aperture 10 is located at the front end of the micro-projector, forming a virtual exit pupil. This reduces the distance between the virtual exit pupil and the waveguide coupling grating, thereby reducing the diffusion of the light spot emitted from the first lens 20, which is beneficial for improving the uniformity of the optical waveguide display and enhancing the display effect. Four lenses are arranged between the virtual aperture 10 and the image source surface 60. The first lens 20 and the third lens 40 both have positive optical power, while the second lens 30 and the fourth lens 50 both have negative optical power. This design creates a projection lens with a small total optical length, a large light-passing aperture, and high light efficiency, which can project a brighter and better-looking image under rated power consumption. The virtual exit pupil micro-projection lens disclosed in this embodiment reduces the size and enhances the near-eye display effect, which is beneficial for combining the virtual exit pupil micro-projection lens with Micro LED to manufacture lightweight, ultra-high-definition head-mounted augmented reality devices.

[0138] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other.

[0139] It should be noted that this invention uses a virtual exit pupil micro-projection lens as an example to introduce the specific structure and working principle of the invention, but the application of this invention is not limited to virtual exit pupil micro-projection lenses, and can also be applied to the production and use of other similar workpieces.

[0140] It should be understood that the present invention is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

[0141] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A virtual exit pupil miniature projection lens, characterized in that, Along the same optical axis, a virtual aperture, a first lens, a second lens, a third lens, a fourth lens, and an image source surface are arranged sequentially from the imaging side to the image source side. The first lens and the third lens both have positive optical power; the second lens and the fourth lens both have negative optical power. The effective focal length of the projection lens is EFL, the distance between the center point of the imaging side surface of the first lens and the image source surface is TTL, the distance between the virtual exit pupil center of the projection lens and the center point of the imaging side surface of the first lens is ENPP, and the virtual exit pupil diameter of the projection lens is ENPD, satisfying the following relationship: ； ； 。 2. The virtual exit pupil miniature projection lens according to claim 1, characterized in that, The fourth lens has at least one inflection point on the image source side.

3. The virtual exit pupil miniature projection lens according to claim 1, characterized in that, The virtual exit pupil micro-projection lens includes a screen protection lens, which is disposed between the fourth lens and the image source surface along the same optical axis.

4. The virtual exit pupil miniature projection lens according to claim 1, characterized in that, The first lens is a glass lens; the second lens, the third lens, and the fourth lens are all plastic lenses.

5. The virtual exit pupil miniature projection lens according to claim 4, characterized in that, The refractive index of the first lens The Abbe number of the first lens is The refractive index of the second lens is The Abbe number of the second lens is The refractive index of the third lens is... The Abbe number of the third lens is The refractive index of the fourth lens is... The Abbe number of the fourth lens is The following relationship must be satisfied: ， ； ， ； ， ； ， 。 6. The virtual exit pupil miniature projection lens according to claim 4, characterized in that, The optical focal length of the projection lens is: The optical power of the first lens is The optical power of the second lens is The optical power of the third lens is It satisfies the following relation: ； 。 7. The virtual exit pupil miniature projection lens according to claim 4, characterized in that, The distance between the center point of the image source side of the first lens and the center point of the image imaging side of the second lens is... The distance from the center point of the image source side of the third lens to the center point of the image imaging side of the fourth lens is It satisfies the following relationship: 。 8. The virtual exit pupil miniature projection lens according to claim 1, characterized in that, Half of the field of view of the projection lens along the diagonal direction is The distance between the center point of the image source side surface of the fourth lens and the image source surface is BFL, which satisfies the following relationship: ； 。 9. The virtual exit pupil miniature projection lens according to claim 1, characterized in that, The curvature of the center point of the surface on the imaging side of the first lens is C. 11 The curvature of the center point of the surface on the image source side of the first lens is C. 12 It satisfies the following relation: 。 10. The virtual exit pupil miniature projection lens according to claim 1, characterized in that, The curvature of the center point of the surface on the imaging side of the second lens The curvature of the center point of the surface on the image source side of the second lens The curvature of the center point of the surface on the imaging side of the third lens is... The curvature of the center point of the surface on the image source side of the third lens is The following relationship must be satisfied: ， ； ， 。

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