Optical imaging system

Abstract

This application discloses an optical imaging system, including a lens barrel and an imaging assembly and a second spacer element disposed within the lens barrel. The imaging assembly, along the optical axis from a first side to a second side, sequentially includes a linear polarizing film, a reflective polarizing element, a quarter-wave plate, a first lens, a second lens, a third lens, a fourth lens, and a partially reflective layer; wherein the first and second lenses are cemented together, and the third and fourth lenses are cemented together. The second spacer element is disposed on and in contact with the second side surface of the second lens. The outer diameter D0m of the second side end face of the lens barrel and the outer diameter D2m of the second side surface of the second spacer element satisfy: 4.51mm ≤ D0m - D2m ≤ 5.8mm; the inner diameter d2m of the second side surface of the second spacer element, the inner diameter d2s of the first side surface of the second spacer element, and the axial distance T23 from the second side surface of the second lens to the first side surface of the third lens satisfy: 0.97 ≤ (d2m - d2s) / T23 ≤ 2.79.

Description

Technical Field

[0001] This application relates to the field of optical devices, and more specifically to an optical imaging system. Background Technology

[0002] With the introduction of the metaverse concept, people have placed higher demands on the optical imaging systems of virtual reality or augmented reality devices. Optical imaging systems are mainly divided into three types: optical systems using aspherical lenses, optical systems using Fresnel lenses, and catadioptric optical systems. Among them, catadioptric optical systems represent a major innovation in optical imaging systems themselves and reserve space for the overall design of virtual reality or augmented reality devices, thus becoming the mainstream trend in research and development.

[0003] Catadioptric optical systems shorten the overall length of the optical imaging system by folding the optical path, thereby shifting the center of gravity of virtual reality or augmented reality devices to the rear and improving the user experience. However, existing catadioptric optical systems typically use two lenses, which can lead to significant ghosting. Summary of the Invention

[0004] This application provides an optical imaging system comprising a lens barrel and an imaging assembly and a second spacer element disposed within the lens barrel. The imaging assembly, along the optical axis from a first side to a second side, sequentially includes a linear polarizing film, a reflective polarizing element, a quarter-wave plate, a first lens, a second lens, a third lens, a fourth lens, and a partially reflective layer; wherein the first and second lenses are cemented together, and the third and fourth lenses are cemented together. The second spacer element is disposed on and in contact with the second side surface of the second lens. The optical imaging system has four lenses with optical power. The outer diameter D0m of the second side end face of the lens barrel and the outer diameter D2m of the second side surface of the second spacer element satisfy: 4.51mm ≤ D0m - D2m ≤ 5.8mm; the inner diameter d2m of the second side surface of the second spacer element, the inner diameter d2s of the first side surface of the second spacer element, and the axial distance T23 from the second side surface of the second lens to the first side surface of the third lens satisfy: 0.97 ≤ (d2m - d2s) / T23 ≤ 2.79.

[0005] According to an exemplary embodiment of this application, the radius of curvature R4 of the second side of the second lens, the outer diameter D2s of the first side of the second spacer element and the refractive index N2 of the second lens satisfy: -2.78≤R4 / (D2s×N2)≤-1.8.

[0006] According to an exemplary embodiment of this application, the maximum thickness CP2 of the second spacer element, the distance EP02 between the first side end face of the lens barrel and the second spacer element along the optical axis and the axial distance T23 between the second side surface of the second lens and the first side surface of the third lens satisfy: 4.46≤(CP2+EP02) / T23≤7.72.

[0007] According to an exemplary embodiment of this application, the center thickness CT3 of the third lens on the optical axis, the center thickness CT4 of the fourth lens on the optical axis, the distance L between the first side end face and the second side end face of the lens barrel along the optical axis and the distance EP02 between the first side end face and the second spacer element along the optical axis satisfy: 0.72≤(CT3+CT4) / (L-EP02)≤1.4.

[0008] According to an exemplary embodiment of this application, the radius of curvature R5 of the first side of the third lens and the inner diameter d2m of the second side of the second spacer element satisfy: 4.45≤R5 / d2m≤5.45.

[0009] According to an exemplary embodiment of this application, the effective focal length f2 of the second lens and the distance EP02 along the optical axis between the first side end face of the lens barrel and the second spacer element satisfy: -25.74≤f2 / EP02≤-15.8.

[0010] According to an exemplary embodiment of this application, the radius of curvature R2 of the second side surface of the first lens and the inner diameter d2s of the first side surface of the second spacer element satisfy: -2.00≤R2 / d2s≤-1.15.

[0011] According to an exemplary embodiment of this application, the radius of curvature R6 of the second side surface of the third lens and the inner diameter d0m of the second side end face of the lens barrel satisfy: 0.88≤R6 / d0m≤1.27.

[0012] According to an exemplary embodiment of this application, the distance L between the first side end face and the second side end face of the lens barrel along the optical axis, the center thickness CT1 of the first lens on the optical axis and the center thickness CT2 of the second lens on the optical axis satisfy: 2.53≤L / (CT1+CT2)≤3.89.

[0013] According to an exemplary embodiment of this application, the combined focal length f34 of the third lens and the fourth lens satisfies the following condition with respect to the outer diameter D0m of the second side end face of the lens barrel: 1.57≤f34 / D0m≤2.69.

[0014] According to an exemplary embodiment of this application, a first lens has positive or negative optical power, its first side surface is concave or flat, and its second side surface is convex. A second lens has negative optical power, and its second side surface is convex. A third lens has negative optical power, its first side surface is convex, and its second side surface is concave. A fourth lens has positive optical power, and its first side surface is convex, and its second side surface is convex.

[0015] The optical imaging system provided in this application employs four lenses. By controlling the difference between the outer diameter of the second side end face of the lens barrel and the outer diameter of the second side face of the second spacer element, ghosting in the optical imaging system can be reduced. However, in this case, the center thickness of the second lens is limited, resulting in decreased assembly stability of the second lens, worse field curvature of the optical imaging system, and affecting the imaging quality of the optical imaging system. Therefore, by rationally configuring the relationship between the inner diameter of the second side face of the second spacer element, the inner diameter of the first side face of the second spacer element, and the axial distance between the second side face of the second lens and the first side face of the third lens, the assembly stability of the second lens can be improved, the assembly deformation of the second lens can be reduced, the field curvature of the optical imaging system can be reduced, and the imaging quality of the optical imaging system can be improved. Attached Figure Description

[0016] Other features, objects, and advantages of this application will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings. Wherein:

[0017] Figure 1 A parameter annotation diagram of an optical imaging system according to this application is shown;

[0018] Figure 2 A schematic diagram of the optical path of the optical imaging system according to this application is shown;

[0019] Figure 3 A schematic diagram of the structure of an optical imaging system according to Embodiment 1 of this application is shown;

[0020] Figure 4 A schematic diagram of the structure of an optical imaging system according to Embodiment 2 of this application is shown;

[0021] Figure 5 A schematic diagram of the structure of an optical imaging system according to Embodiment 3 of this application is shown;

[0022] Figure 6 , Figure 7 , Figure 8 The on-axis chromatic aberration curves, astigmatism curves, and distortion curves of the optical imaging systems according to embodiments 1, 2, and 3 of this application are shown.

[0023] Figure 9 A schematic diagram of the structure of an optical imaging system according to Embodiment 4 of this application is shown;

[0024] Figure 10 A schematic diagram of the structure of an optical imaging system according to Embodiment 5 of this application is shown;

[0025] Figure 11 A schematic diagram of the structure of an optical imaging system according to Embodiment 6 of this application is shown;

[0026] Figure 12 , Figure 13 , Figure 14 The on-axis chromatic aberration curves, astigmatism curves, and distortion curves of the optical imaging systems according to embodiments 4, 5, and 6 of this application are shown.

[0027] Figure 15 A schematic diagram of the structure of an optical imaging system according to Embodiment 7 of this application is shown;

[0028] Figure 16 A schematic diagram of the structure of an optical imaging system according to Embodiment 8 of this application is shown;

[0029] Figure 17 A schematic diagram of the structure of an optical imaging system according to Embodiment 9 of this application is shown;

[0030] Figure 18 , Figure 19 , Figure 20 On-axis chromatic aberration curves, astigmatism curves, and distortion curves of optical imaging systems according to embodiments 7, 8, and 9 of this application are shown. Detailed Implementation

[0031] To better understand this application, various aspects of this application will be described in more detail with reference to the accompanying drawings. It should be understood that these detailed descriptions are merely illustrative of exemplary embodiments of this application and are not intended to limit the scope of this application in any way. Throughout the specification, the same reference numerals refer to the same elements. The expression "and / or" includes any and all combinations of one or more of the associated listed items.

[0032] It should be noted that in this specification, the terms "first," "second," "third," etc., are used only to distinguish one feature from another and do not imply any limitation on the features. Therefore, without departing from the teachings of this application, the first lens discussed below may also be referred to as the second lens or the third lens.

[0033] In the accompanying drawings, the thickness, size, and shape of the lenses have been slightly exaggerated for ease of illustration. Specifically, the shapes of the spherical or aspherical surfaces shown in the drawings are illustrated by way of example. That is, the shapes of the spherical or aspherical surfaces are not limited to those shown in the drawings. The drawings are for illustrative purposes only and are not drawn strictly to scale.

[0034] In this paper, the paraxial region refers to the region near the optical axis. If the lens surface is convex and the location of the convexity is not defined, it means that the lens surface is convex at least in the paraxial region; if the lens surface is concave and the location of the concaveness is not defined, it means that the lens surface is concave at least in the paraxial region. The surface of each lens closest to the first side (e.g., the human eye side) is called the first side surface of the lens, and the surface of each lens closest to the second side (e.g., the display screen side) is called the second side surface of the lens.

[0035] The optical imaging system of the exemplary embodiments of this application can be simulated using software and / or tools such as ZEMAX and CODEV. Optionally, the optical imaging system can be simulated using CODEV software. During the simulation process using software and / or tools as described above, the surface profile of each lens can be appropriately adjusted according to the built-in surface profile model of the software and / or tool used.

[0036] It should also be understood that the terms "comprising" and / or "having," when used in this specification, indicate the presence of the stated features, elements, and / or components, but do not exclude the presence or addition of one or more other features, elements, components, and / or combinations thereof. Furthermore, when describing embodiments of this application, the word "may" is used to mean "one or more embodiments of this application." And the term "exemplary" is intended to refer to an example or illustration.

[0037] Unless otherwise specified, all terms used herein (including technical and scientific terms) shall have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. It should also be understood that terms (e.g., those defined in common dictionaries) shall be interpreted as having the meaning consistent with their meaning in the context of the relevant art and shall not be interpreted in an idealized or overly formalized sense, unless expressly so specified herein.

[0038] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0039] Figure 1 This is a parameter annotation diagram according to an exemplary embodiment of this application. Reference Figure 1d0s represents the inner diameter of the first side end face of the lens barrel, D0s represents the outer diameter of the first side end face of the lens barrel, d0m represents the inner diameter of the second side end face of the lens barrel, D0m represents the outer diameter of the second side end face of the lens barrel, d2m represents the inner diameter of the second side surface of the second spacer element, D2m represents the outer diameter of the second side surface of the second spacer element, d2s represents the inner diameter of the first side surface of the second spacer element, D2s represents the outer diameter of the first side surface of the second spacer element, CP2 represents the maximum thickness of the second spacer element, EP02 represents the distance between the first side end face of the lens barrel and the second spacer element along the optical axis, and L represents the distance between the first side end face of the lens barrel and the second side end face of the lens barrel along the optical axis.

[0040] The first aspect of this application provides an optical imaging system that may include an imaging group. The imaging group may include a linear polarizing film, a reflective polarizing element, a quarter-wave plate, a first lens, a second lens, a third lens, a fourth lens, and a partially reflective layer arranged sequentially along the optical axis from a first side to a second side. The optical imaging system has four lenses with optical power. By utilizing the reflective polarizing element, the quarter-wave plate, and the partially reflective layer, optical path reflection can be achieved, effectively shortening the overall length of the optical imaging system, reducing its size and weight, and achieving a lightweight optical imaging system.

[0041] In an exemplary embodiment, the first lens and the second lens are cemented together to form a cemented lens. The third lens and the fourth lens are cemented together to form a cemented lens.

[0042] In an exemplary embodiment, the first lens may have positive or negative optical power. The second lens may have negative optical power. The third lens may have negative optical power. The fourth lens may have positive optical power.

[0043] In an exemplary embodiment, the first side surface of the first lens can be concave or planar, and the second side surface can be convex. Setting the first side surface of the first lens to be concave can increase the maximum field of view of the optical imaging system, thereby increasing the field of view range of the optical imaging system.

[0044] In an exemplary embodiment, the second side surface of the second lens can be convex. When the third lens has a small center thickness, by setting the second side surface of the second lens to be convex, the second side surface of the second lens can converge the light rays, thereby converging the light rays on the image surface of the second side as much as possible, ensuring that the optical imaging system has a small image height, which is beneficial to reducing the size of the display screen on the second side and reducing the weight and cost of the optical imaging system.

[0045] In an exemplary embodiment, the first side surface of the third lens can be a convex surface, and the second side surface can be a concave surface.

[0046] In an exemplary embodiment, the first side surface of the fourth lens can be convex, and the second side surface can also be convex. When the third lens has a small center thickness, by setting the second side surface of the fourth lens to be convex, the second side surface of the fourth lens can converge the light rays, thereby converging the light rays on the image surface of the second side as much as possible. This ensures that the optical imaging system has a small image height, which is beneficial for reducing the size of the display screen on the second side and reducing the weight and cost of the optical imaging system.

[0047] In an exemplary embodiment, a linear polarizing film may be placed on a first side of a reflective polarizing element and at least partially adhered to the first side of the reflective polarizing element. The reflective polarizing element may be placed on a first side of a quarter-wave plate and at least partially adhered to the first side of the quarter-wave plate. The quarter-wave plate may be placed on a first side of a first lens and at least partially adhered to the first side of the first lens.

[0048] In an exemplary embodiment, a partial reflective layer may be placed on the second side of the fourth lens and at least partially adhered to the second side of the fourth lens. The partial reflective layer can have a semi-transmissive and semi-reflective effect on light. By providing a partial reflective layer on the second side of the fourth lens and combining it with a reflective polarizing element and a quarter-wave plate, light can be refracted multiple times, effectively reducing the overall length of the optical imaging system.

[0049] In an exemplary embodiment, the optical imaging system may further include an aperture stop, which may be disposed on a first side of the first lens. As an example, the aperture stop may be, for example, the pupil of a user's eye. Image light from the second side is finally projected onto the user's eye on the first side after multiple refractions and reflections through a partial reflective layer, a fourth lens, a third lens, a second lens, a first lens, a quarter-wave plate, a reflective polarizing element, a linear polarizing film, etc.

[0050] In an exemplary embodiment, the first side may be, for example, the human eye side, and the second side may be, for example, the display screen side. Accordingly, the first side of each element (such as the first lens, second lens, third lens, fourth lens, partial reflective layer, quarter-wave plate, reflective polarizing element, linear polarizing film) may be referred to as the side near the human eye, and the second side may be referred to as the side near the screen.

[0051] In an exemplary embodiment, an image surface may be provided on the second side of the optical imaging system. The image surface may include a display screen. Light from the display screen passes sequentially through a fourth lens, a third lens, a second lens, a first lens, and a quarter-wave plate, reaching a reflective polarizing element, where it is reflected to form a first reflected image light. The first reflected image light passes sequentially through the quarter-wave plate, the first lens, the second lens, the third lens, and the fourth lens, reaching a partial reflective layer on the second side of the fourth lens, where it is reflected to form a second reflected image light. The second reflected image light passes sequentially through the fourth lens, the third lens, the second lens, the first lens, the quarter-wave plate, the reflective polarizing element, and a linear polarizing film to the aperture stop and is finally projected onto the human eye. The optical imaging system provided in this application folds the required optical path without affecting projection quality by combining light reflection and refraction, effectively shortening the overall length of the optical imaging system.

[0052] In an exemplary embodiment, the optical imaging system may further include a second spacer element. The second spacer element may be positioned on a second side surface of the second lens and at least partially in contact with the second side surface of the second lens. Proper use of the spacer element can effectively mitigate stray light risks, reduce interference with image quality, and thereby improve the imaging quality of the optical imaging system.

[0053] In an exemplary embodiment, the optical imaging system may further include a lens barrel. An imaging group and a second spacer element are disposed within the lens barrel. The end face of the lens barrel closest to the first side is the first end face of the lens barrel, and the end face of the lens barrel closest to the second side is the second end face of the lens barrel.

[0054] In an exemplary embodiment, the outer peripheral surface of at least one lens in the imaging group may have a truncated portion and a non-truncated portion, and the outer diameter of the truncated portion of the lens may be smaller than the outer diameter of the non-truncated portion. When the outer peripheral surface of the lens has a truncated portion, the outer diameter of the lens generally refers to the outer diameter of the non-truncated portion. For example, the outer diameter of the first side surface of the lens refers to the outer diameter of the portion of the non-truncated portion closest to the first side, and the outer diameter of the second side surface of the lens refers to the outer diameter of the portion of the non-truncated portion closest to the second side.

[0055] In an exemplary embodiment, the outer peripheral surface of the second spacer element may have a truncated portion and a non-truncated portion, and the outer diameter of the truncated portion of the second spacer element may be smaller than the outer diameter of the non-truncated portion. When the outer peripheral surface of the second spacer element has a truncated portion, the outer diameter of the second spacer element generally refers to the outer diameter of the non-truncated portion. For example, the outer diameter of the first side surface of the second spacer element refers to the outer diameter of the portion of the non-truncated portion of the second spacer element closest to the first side, and the outer diameter of the second side surface of the second spacer element refers to the outer diameter of the portion of the non-truncated portion of the second spacer element closest to the second side.

[0056] In an exemplary embodiment, the outer diameter D0m of the second side end face of the lens barrel and the outer diameter D2m of the second side face of the second spacer element satisfy: 4.51mm ≤ D0m - D2m ≤ 5.8mm; the inner diameter d2m of the second side face of the second spacer element, the inner diameter d2s of the first side face of the second spacer element, and the axial distance T23 from the second side face of the second lens to the first side face of the third lens satisfy: 0.97 ≤ (d2m - d2s) / T23 ≤ 2.79. By controlling the range of the difference between the outer diameter of the second side end face of the lens barrel and the outer diameter of the second side face of the second spacer element, ghosting in the optical imaging system can be reduced. However, in this case, the center thickness of the second lens is limited, resulting in poor assembly stability of the second lens, worse field curvature of the optical imaging system, and affecting the imaging quality of the optical imaging system. Therefore, by rationally configuring the relationship between the inner diameter of the second side of the second spacer element, the inner diameter of the first side of the second spacer element, and the axial distance between the second side of the second lens and the first side of the third lens, the assembly stability of the second lens can be improved, the assembly deformation of the second lens can be reduced, the field curvature of the optical imaging system can be reduced, and the imaging quality of the optical imaging system can be improved.

[0057] Table 1 shows the structural sensitivity analysis of the second side surface of the second lens. Table 2 shows the optical sensitivity and overall sensitivity analysis of the second side surface of the second lens. Lens 1 satisfies (d²m - d²s) / T²³ = 1.26, lens 2 satisfies (d²m - d²s) / T²³ = 0.08, and lens 3 satisfies (d²m - d²s) / T²³ = 7.63.

[0058] In Table 1, surface S4 represents the second side surface of the second lens, and ΔS4PV (i.e., structural sensitivity) represents the change in surface shape of the second side surface of the second lens. Under stress, the center point and edge point of the second side surface of the second lens will shift, resulting in a change in the surface shape PV of the second side surface. The smaller the absolute value of ΔS4PV, the smaller the change in surface shape of the second side surface of the second lens, and the better the structural sensitivity of the second side surface of the second lens. The center point and edge point of the second side surface of the second lens can be referenced... Figure 1 .

[0059] In Table 2, the peak value in the S-direction can be the peak value of the S-curve of the MTF curve at a field of view of 0.4, and the peak value in the M-direction can be the peak value of the M-curve of the MTF curve at a field of view of 0.4. "S" represents the sagittal curve, and "M" represents the meridional curve. When ΔS4PV changes, the peak values ​​in the S-direction and / or M-direction will change accordingly. The amount of change in the peak values ​​in the S-direction and / or M-direction can be considered the optical sensitivity. The overall sensitivity can be the product of the structural sensitivity and the optical sensitivity. It should be understood that the smaller the absolute value of the optical sensitivity, the better the optical sensitivity; the smaller the absolute value of the overall sensitivity, the better the overall sensitivity. Here, MTF stands for Modulation Transfer Function.

[0060]

[0061]

[0062] Table 1

[0063]

[0064] Table 2

[0065] Structural sensitivity represents the change in surface shape of the second side surface of the lens when a certain load is applied to the lens. When the same load is applied to lenses 1, 2, and 3, and the second side surface of each lens is subjected to the same external force, the center point and edge point of the second side surface of the second lens will shift under the influence of stress, thus causing a change in the surface shape PV of the second side surface. For example, referring to Table 1, through simulation, the structural sensitivity of lenses 1, 2, and 3 are 0.0188 μm, 0.783 μm, and 0.190 μm, respectively. It can be seen that lens 1 has a smaller structural sensitivity, meaning a smaller change in surface shape, and therefore, lens 1 has superior structural sensitivity.

[0066] Optical sensitivity represents the change in the peak MTF of a lens when the lens profile changes by a constant amount. Lenses 1, 2, and 3 have the same amount of profile change. For example, referring to Table 2, through simulation, when ΔS4PV increases by 1µm, the changes in the peak MTF in the S-direction at 0.4 field of view for lenses 1, 2, and 3 are -0.46%, -0.66%, and -0.91%, respectively, and the changes in the peak MTF in the M-direction at 0.4 field of view are -0.38%, -0.83%, and -0.61%, respectively. When ΔS4PV decreases by 1µm, the changes in the peak MTF in the S-direction at 0.4 field of view for lenses 1, 2, and 3 are 0.95%, 0.46%, and 0.63%, respectively, and the changes in the peak MTF in the M-direction at 0.4 field of view are 0.81%, 0.49%, and 0.47%, respectively. It can be seen that the peak MTF of lens 1 is less affected by the profile change, and lens 1 has better optical sensitivity.

[0067] Overall sensitivity represents the effect of surface shape change on the peak MTF of the lens. For example, referring to Table 2, the overall sensitivity in the S direction of lens 1, lens 2, and lens 3 are -0.00865μm, -0.517μm, and -0.173μm, respectively, and the overall sensitivity in the M direction are -0.00714μm, -0.650μm, and -0.116μm, respectively. It can be seen that the surface shape change of lens 1 is smaller, and the effect of surface shape change on the peak MTF is smaller. Therefore, lens 1 has a lower overall sensitivity and better assembly stability.

[0068] Based on the above analysis, it can be seen that by ensuring that the optical imaging system satisfies "0.97≤(d2m-d2s) / T23≤2.79", the second side of the second lens can have a small change in surface shape, reducing the structural sensitivity and optical sensitivity of the optical imaging system, thereby reducing the overall sensitivity of the optical imaging system and improving the assembly stability of the optical imaging system.

[0069] In an exemplary embodiment, the radius of curvature R4 of the second side surface of the second lens, the outer diameter D2s of the first side surface of the second spacer element, and the refractive index N2 of the second lens satisfy: -2.78 ≤ R4 / (D2s×N2) ≤ -1.8. By controlling the above conditional expression, the focal length of the second lens can be constrained within a certain range, thereby controlling the exit angle of the light emitted from the second lens and reducing the incident angle of the light on the display screen; at the same time, the outer diameter of the first side surface of the second spacer element can also be limited, improving the manufacturability of the second spacer element.

[0070] In an exemplary embodiment, the maximum thickness CP2 of the second spacer element, the distance EP02 between the first side end face of the lens barrel and the second spacer element along the optical axis, and the axial distance T23 between the second side surface of the second lens and the first side surface of the third lens satisfy: 10.07 ≤ (CP2 + EP02) / T23 ≤ 15.74. By controlling the above conditional expression, the center thickness and edge thickness of the second and third lenses can be constrained within a reasonable range. While ensuring good manufacturability of the second and third lenses, the assembly stability of the two cemented lenses is improved. At the same time, the axial distance between the second side surface of the second lens and the first side surface of the third lens can be limited, effectively correcting field curvature and improving the imaging quality of the optical imaging system.

[0071] In an exemplary embodiment, the center thickness CT3 of the third lens on the optical axis, the center thickness CT4 of the fourth lens on the optical axis, the distance L between the first and second end faces of the lens barrel along the optical axis, and the distance EP02 between the first end face of the lens barrel and the second spacer element along the optical axis satisfy the following condition: 0.72 ≤ (CT3 + CT4) / (L - EP02) ≤ 1.4. By controlling the above conditional expression, the thickness ratio of the third and fourth lenses can be constrained within a reasonable range, which is beneficial to the molding and bonding of the third and fourth lenses; at the same time, it can also limit the distance between the first and second end faces of the lens barrel along the optical axis, reduce the overall length of the optical imaging system, reduce the weight of the optical imaging system, realize the miniaturization of the optical imaging system, and improve the user's wearing experience.

[0072] In an exemplary embodiment, the radius of curvature R5 of the first side of the third lens and the inner diameter d2m of the second side of the second spacer element satisfy: 4.45 ≤ R5 / d2m ≤ 5.45. By rationally configuring the ratio of the radius of curvature of the first side of the third lens to the inner diameter of the second side of the second spacer element, the overall shape of the third lens can be constrained, the sensitivity of the third lens reduced, and the assembly yield of the third lens improved. Simultaneously, it allows the refractive power of the second spacer element and the third lens to match, minimizing the obstruction of effective light by the second spacer element while blocking ineffective light rays, reducing stray light, and improving the light efficiency of the optical imaging system.

[0073] In an exemplary embodiment, the effective focal length f2 of the second lens and the distance EP02 along the optical axis between the first side end face of the lens barrel and the second spacer element satisfy: -25.74 ≤ f2 / EP02 ≤ -15.8. By controlling the above conditional expression, the optical power of the second lens can be reasonably allocated, effectively constraining the aberration contribution of the second lens, so that the aberration generated by the second lens is balanced with the aberration generated by other optical elements, ensuring that the aberration of the optical imaging system is at a reasonable level; at the same time, the maximum thickness of the second spacer element can be limited, so that the second spacer element and the adjacent lens are stably supported, improving the assembly stability and assembly yield of the optical imaging system.

[0074] In an exemplary embodiment, the radius of curvature R2 of the second side surface of the first lens and the inner diameter d2s of the first side surface of the second spacer element satisfy: -2.00 ≤ R2 / d2s ≤ -1.15. By controlling the above conditional expression, the overall shape of the first lens can be constrained, which is beneficial to reducing the sensitivity of the first lens and improving the assembly yield of the first lens; at the same time, it can also make the refractive degree of the second spacer element and the first lens match, so that while the second spacer element intercepts ineffective light, it minimizes the obstruction of effective light by the second spacer element, reduces stray light, and improves the light efficiency of the optical imaging system.

[0075] In an exemplary embodiment, the radius of curvature R6 of the second side surface of the third lens and the inner diameter d0m of the second side end face of the lens barrel satisfy the condition: 0.88≤R6 / d0m≤1.27. By controlling the above condition, the overall shape of the third lens can be constrained, which is beneficial to reducing the sensitivity of the third lens and improving the assembly yield of the third lens; at the same time, it can also ensure that the refractive power of the lens barrel and the third lens are matched, so that when the lens barrel intercepts non-effective light rays, it minimizes the obstruction of effective light rays by the lens barrel, reduces stray light, and improves the light efficiency of the optical imaging system. In addition, it is also beneficial to the shaping of the lens barrel and the feasibility of assembling the third lens.

[0076] In an exemplary embodiment, the distance L between the first and second end faces of the lens barrel along the optical axis, and the center thickness CT1 and center thickness CT2 of the first and second lenses along the optical axis satisfy the following: 2.53 ≤ L / (CT1+CT2) ≤ 3.89. By controlling the ratio of the distance between the first and second end faces of the lens barrel along the optical axis to the sum of the center thicknesses of the first and second lenses within a certain range, it is beneficial to reduce the total optical length of the optical imaging system and achieve miniaturization of the optical imaging system.

[0077] In an exemplary embodiment, the combined focal length f34 of the third and fourth lenses satisfies the condition 1.57 ≤ f34 / D0m ≤ 2.69 with respect to the outer diameter D0m of the second side end face of the lens barrel. By controlling the above condition, the combined focal length of the third and fourth lenses can be constrained within a reasonable range, causing the cemented lens formed by the cementing of the third and fourth lenses to produce negative spherical aberration, which is then balanced with the positive spherical aberration produced by other lenses, thereby improving the imaging quality of the optical imaging system. Simultaneously, the outer diameter of the second side end face of the lens barrel can be limited, ensuring its limiting effect on the fourth lens while improving the manufacturability of the lens barrel.

[0078] The optical imaging system according to the above embodiments of this application can employ multiple lenses, such as the four lenses described above. By rationally allocating the parameters of the linear polarizing film, reflective polarizing element, quarter-wave plate, partial reflective layer, each lens, lens barrel, and second spacer element, the overall length of the optical imaging system can be reduced, improving its manufacturability, assembly stability, and imaging quality. The optical imaging system configured as described above features miniaturization and good imaging quality, effectively meeting the usage needs of various portable electronic products in projection scenarios. Furthermore, the center of gravity of the optical imaging system and the electronic device containing it is shifted rearward, improving the user's wearing experience.

[0079] In an exemplary embodiment, at least one of the surfaces of the first to fourth lenses is an aspherical surface. An aspherical lens is characterized by a continuously changing curvature from its center to its periphery. Unlike a spherical lens, which has a constant curvature from its center to its periphery, an aspherical lens has superior curvature radius characteristics, offering advantages in improving distortion and astigmatism. By using an aspherical lens, aberrations occurring during imaging can be eliminated as much as possible, thereby improving image quality.

[0080] A second aspect of this application provides an optical imaging system that may include a lens barrel and an imaging assembly mounted within the lens barrel. The imaging assembly may sequentially include, from a first side to a second side along the optical axis, a linear polarizing film, a reflective polarizing element, a quarter-wave plate, a first lens, a second lens, a third lens, a fourth lens, and a partially reflective layer. The optical imaging system has four lenses with optical power.

[0081] The combined focal length f34 of the third and fourth lenses satisfies the condition 1.57 ≤ f34 / D0m ≤ 2.69 with respect to the outer diameter D0m of the second side end face of the lens barrel. By controlling the above condition, the combined focal length of the third and fourth lenses can be constrained within a reasonable range, allowing the cemented lens formed by the cemented third and fourth lenses to produce negative spherical aberration, which is then balanced with the positive spherical aberration produced by other lenses, thereby improving the imaging quality of the optical imaging system. Simultaneously, the outer diameter of the second side end face of the lens barrel can be limited, ensuring its role in limiting the fourth lens while improving the manufacturability of the lens barrel.

[0082] Those skilled in the art will understand that, without departing from the technical solutions claimed in this application, the number of lenses and spacers constituting the optical imaging system can be changed to obtain the various results and advantages described in this specification.

[0083] Specific embodiments of the optical imaging system applicable to the above-described embodiments are further described below with reference to the accompanying drawings.

[0084] Example 1

[0085] The following is for reference Figure 2 and Figure 3 Describes an optical imaging system according to Embodiment 1 of this application. In this system, the aperture stop STO and the image plane IMA are not located... Figure 3 As shown in the image.

[0086] like Figure 3 As shown, the optical imaging system may include a lens barrel P0 and an imaging assembly and a second spacer element P2 assembled within the lens barrel P0. The imaging assembly includes a linear polarizing film LP, a reflective polarizing element RP, a quarter-wave plate QWP, a first lens E1, a second lens E2, a third lens E3, a fourth lens E4, and a partially reflective layer BS, arranged sequentially along the optical axis from the first side to the second side. An aperture stop STO is positioned between the first side and the linear polarizing film LP (e.g., ...). Figure 2 ).

[0087] The first lens E1 has positive optical power, with its first side surface S1 being planar and its second side surface S2 being convex. The second lens E2 has negative optical power, with its first side surface S3 being concave and its second side surface S4 being convex. The third lens E3 has negative optical power, with its first side surface S5 being convex and its second side surface S6 being concave. The fourth lens E4 has positive optical power, with its first side surface S7 being convex and its second side surface S8 being convex. A linear polarizing film LP, a reflective polarizing element RP, and a quarter-wave plate QWP are attached to the first side surface S1 of the first lens E1. A partially reflective layer BS is attached to the second side surface S8 of the fourth lens E4.

[0088] In this example, an image plane IMA (such as an image plane IMA) can be provided on the second side of the optical imaging system. Figure 2The image plane IMA may, for example, be equipped with a display screen. Light from the image plane IMA passes sequentially through the fourth lens E4, the third lens E3, the second lens E2, the first lens E1, and the quarter-wave plate QWP, reaching the reflective polarizing element RP, where it is reflected to form the first reflected image light. The first reflected image light passes sequentially through the quarter-wave plate QWP, the first lens E1, the second lens E2, the third lens E3, and the fourth lens E4, reaching the partial reflective layer BS on the second side of the fourth lens, where it is reflected to form the second reflected image light. The second reflected image light passes sequentially through the fourth lens E4, the third lens E3, the second lens E2, the first lens E1, the quarter-wave plate QWP, the reflective polarizing element RP, the linear polarizing film LP, to the aperture stop STO, and is finally projected onto the human eye. For example, the light from this optical imaging system, after two reflections, is finally projected onto the human eye.

[0089] Table 3 shows the basic parameters of the optical imaging system of Example 1, where the units for radius of curvature and thickness / distance are millimeters (mm).

[0090]

[0091] Table 3

[0092] In this embodiment, the effective focal length f2 of the second lens is -118.55mm, and the combined focal length f34 of the third and fourth lenses is 126.88mm.

[0093] The object-side surface and image-side surface of any one of the second side surfaces S2 of the first lens E1 to S8 of the fourth lens E4 are aspherical. The surface shape of each aspherical lens can be defined using, but is not limited to, the following aspherical formula:

[0094]

[0095] Where x is the distance vector from the vertex of the aspherical surface at a height of h along the optical axis; c is the paraxial curvature of the aspherical surface, c = 1 / R (i.e., the paraxial curvature c is the reciprocal of the radius of curvature R in Table 3 above); k is the conic coefficient; Ai is the i-th order correction coefficient of the aspherical surface. Table 4 gives the conic coefficient k and higher-order coefficients A4, A6, A8, A10, A12 and A14 that can be used for each aspherical surface S2-S8 in Example 1.

[0096]

[0097]

[0098] Table 4

[0099] Example 2

[0100] The following is for reference Figure 2 and Figure 4 Describes an optical imaging system according to Embodiment 2 of this application. In this system, the aperture stop STO and the image plane IMA are not located... Figure 4 As shown in the image.

[0101] like Figure 4 As shown, the optical imaging system may include a lens barrel P0 and an imaging assembly and a second spacer element P2 assembled within the lens barrel P0. The imaging assembly includes a linear polarizing film LP, a reflective polarizing element RP, a quarter-wave plate QWP, a first lens E1, a second lens E2, a third lens E3, a fourth lens E4, and a partially reflective layer BS, arranged sequentially along the optical axis from the first side to the second side. An aperture stop STO is positioned between the first side and the linear polarizing film LP (e.g., ...). Figure 2 ).

[0102] The structure of the imaging group in this embodiment is the same as that in Embodiment 1. That is, the basic parameter table of the optical imaging system in this embodiment is the same as that in Table 3, and the aspherical coefficient table is the same as that in Table 4. The difference between this embodiment and Embodiment 1 lies in the structural dimensions and other parameters of the lens barrel P0 and the second spacer element P2. The values ​​of multiple parameters of the lens barrel P0 and the second spacer element P2 included in the optical imaging systems of this embodiment and Embodiment 1 are shown in Table 9 below.

[0103] Example 3

[0104] The following is for reference Figure 2 and Figure 5 Describes an optical imaging system according to Embodiment 3 of this application. In this system, the aperture stop STO and the image plane IMA are not located... Figure 5 As shown in the image.

[0105] like Figure 5 As shown, the optical imaging system may include a lens barrel P0 and an imaging assembly and a second spacer element P2 assembled within the lens barrel P0. The imaging assembly includes a linear polarizing film LP, a reflective polarizing element RP, a quarter-wave plate QWP, a first lens E1, a second lens E2, a third lens E3, a fourth lens E4, and a partially reflective layer BS, arranged sequentially along the optical axis from the first side to the second side. An aperture stop STO is positioned between the first side and the linear polarizing film LP (e.g., ...). Figure 2 ).

[0106] The structure of the imaging group in this embodiment is the same as that in Embodiment 1. That is, the basic parameter table of the optical imaging system in this embodiment is the same as that in Table 3, and the aspherical coefficient table is the same as that in Table 4. The difference between this embodiment and Embodiment 1 lies in the structural dimensions and other parameters of the lens barrel P0 and the second spacer element P2. The values ​​of multiple parameters of the lens barrel P0 and the second spacer element P2 included in the optical imaging systems of this embodiment and Embodiment 1 are shown in Table 9 below.

[0107] Figure 6 The on-axis chromatic aberration curves of the optical imaging systems of Examples 1, 2 and 3 are shown, which represent the deflection of the focal point after light of different wavelengths passes through the optical imaging system. Figure 7 Astigmatism curves of the optical imaging systems of Examples 1, 2 and 3 are shown, representing the meridional and sagittal image plane curvatures corresponding to different half-field angles. Figure 8 The distortion curves of the optical imaging systems of Examples 1, 2, and 3 are shown, representing the distortion magnitude values ​​corresponding to different half-field angles. According to... Figures 6 to 8 It can be seen that the optical imaging systems given in Examples 1, 2 and 3 can achieve good imaging quality.

[0108] Example 4

[0109] The following is for reference Figure 2 and Figure 9 Describes an optical imaging system according to Embodiment 4 of this application. In this system, the aperture stop STO and the image plane IMA are not located... Figure 9 As shown in the image.

[0110] like Figure 9 As shown, the optical imaging system may include a lens barrel P0 and an imaging assembly and a second spacer element P2 assembled within the lens barrel P0. The imaging assembly includes a linear polarizing film LP, a reflective polarizing element RP, a quarter-wave plate QWP, a first lens E1, a second lens E2, a third lens E3, a fourth lens E4, and a partially reflective layer BS, arranged sequentially along the optical axis from the first side to the second side. An aperture stop STO is positioned between the first side and the linear polarizing film LP (e.g., ...). Figure 2 ).

[0111] The first lens E1 has negative optical power, with its first side surface S1 being concave and its second side surface S2 being convex. The second lens E2 has negative optical power, with its first side surface S3 being concave and its second side surface S4 being convex. The third lens E3 has negative optical power, with its first side surface S5 being convex and its second side surface S6 being concave. The fourth lens E4 has positive optical power, with its first side surface S7 being convex and its second side surface S8 being convex. A linear polarizing film LP, a reflective polarizing element RP, and a quarter-wave plate QWP are attached to the first side surface S1 of the first lens E1. A partially reflective layer BS is attached to the second side surface S8 of the fourth lens E4.

[0112] In this example, an image plane IMA (such as an image plane IMA) can be provided on the second side of the optical imaging system. Figure 2 The image plane IMA may, for example, be equipped with a display screen. Light from the image plane IMA passes sequentially through the fourth lens E4, the third lens E3, the second lens E2, the first lens E1, and the quarter-wave plate QWP, reaching the reflective polarizing element RP, where it is reflected to form the first reflected image light. The first reflected image light passes sequentially through the quarter-wave plate QWP, the first lens E1, the second lens E2, the third lens E3, and the fourth lens E4, reaching the partial reflective layer BS on the second side of the fourth lens, where it is reflected to form the second reflected image light. The second reflected image light passes sequentially through the fourth lens E4, the third lens E3, the second lens E2, the first lens E1, the quarter-wave plate QWP, the reflective polarizing element RP, the linear polarizing film LP to the aperture stop STO, and is finally projected onto the human eye. For example, the light from this optical imaging system, after two reflections, is finally projected onto the human eye.

[0113] Table 5 shows the basic parameters of the optical imaging system of Example 4, where the units for radius of curvature and thickness / distance are millimeters (mm).

[0114]

[0115] Table 5

[0116] In this embodiment, the effective focal length f2 of the second lens is -193.08mm, and the combined focal length f34 of the third and fourth lenses is 75.94mm.

[0117] The object side and image side of any one of the second side surfaces S2 of the first lens E1 to the second side surface S8 of the fourth lens E4 are aspherical. Table 6 gives the conic coefficient k and higher-order coefficients A4, A6, A8, A10, A12, A14 and A16 that can be used for each aspherical surface S2-S8 in Example 4.

[0118] Face number k A4 A6 A8 A10 A12 A14 A16 S2 / S3 5.0699 3.12E-05 -1.41E-08 -3.19E-10 4.35E-12 -1.96E-14 3.35E-17 -1.36E-20 S4 8.6089 1.04E-05 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 S5 -973.0233 1.00E-05 -3.24E-09 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 S6 / S7 100.0000 1.50E-05 -3.02E-08 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 S8 0.4203 -3.65E-05 2.01E-08 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00

[0119] Table 6

[0120] Example 5

[0121] The following is for reference Figure 2 and Figure 10 Describes an optical imaging system according to Embodiment 5 of this application. In this system, the aperture stop STO and the image plane IMA are not located... Figure 10 As shown in the image.

[0122] like Figure 10As shown, the optical imaging system may include a lens barrel P0 and an imaging assembly and a second spacer element P2 assembled within the lens barrel P0. The imaging assembly includes a linear polarizing film LP, a reflective polarizing element RP, a quarter-wave plate QWP, a first lens E1, a second lens E2, a third lens E3, a fourth lens E4, and a partially reflective layer BS, arranged sequentially along the optical axis from the first side to the second side. An aperture stop STO is positioned between the first side and the linear polarizing film LP (e.g., ...). Figure 2 ).

[0123] The structure of the imaging group in this embodiment is the same as that in Embodiment 4. That is, the basic parameter table of the optical imaging system in this embodiment is the same as that in Table 5, and the aspherical coefficient table is the same as that in Table 6. The difference between this embodiment and Embodiment 4 lies in the structural dimensions and other parameters of the lens barrel P0 and the second spacer element P2. The values ​​of multiple parameters of the lens barrel P0 and the second spacer element P2 included in the optical imaging systems of this embodiment and Embodiment 4 are shown in Table 9 below.

[0124] Example 6

[0125] The following is for reference Figure 2 and Figure 11 Describes an optical imaging system according to Embodiment 6 of this application. In this system, the aperture stop STO and the image plane IMA are not located... Figure 11 As shown in the image.

[0126] like Figure 11 As shown, the optical imaging system may include a lens barrel P0 and an imaging assembly and a second spacer element P2 assembled within the lens barrel P0. The imaging assembly includes a linear polarizing film LP, a reflective polarizing element RP, a quarter-wave plate QWP, a first lens E1, a second lens E2, a third lens E3, a fourth lens E4, and a partially reflective layer BS, arranged sequentially along the optical axis from the first side to the second side. An aperture stop STO is positioned between the first side and the linear polarizing film LP (e.g., ...). Figure 2 ).

[0127] The structure of the imaging group in this embodiment is the same as that in Embodiment 4. That is, the basic parameter table of the optical imaging system in this embodiment is the same as that in Table 5, and the aspherical coefficient table is the same as that in Table 6. The difference between this embodiment and Embodiment 4 lies in the structural dimensions and other parameters of the lens barrel P0 and the second spacer element P2. The values ​​of multiple parameters of the lens barrel P0 and the second spacer element P2 included in the optical imaging systems of this embodiment and Embodiment 4 are shown in Table 9 below.

[0128] Figure 12 The on-axis chromatic aberration curves of the optical imaging systems of Examples 4, 5 and 6 are shown, which represent the deflection of the focal point after light of different wavelengths passes through the optical imaging system. Figure 13Astigmatism curves for the optical imaging systems of Examples 4, 5, and 6 are shown, representing the meridional and sagittal image plane curvatures corresponding to different half-field angles. Figure 14 The distortion curves of the optical imaging systems of Examples 4, 5, and 6 are shown, representing the distortion magnitude values ​​corresponding to different half-field angles. According to... Figures 12 to 14 It can be seen that the optical imaging systems given in Examples 4, 5 and 6 can achieve good imaging quality.

[0129] Example 7

[0130] The following is for reference Figure 2 and Figure 15 The optical imaging system according to Embodiment 7 of this application is described. In this system, the aperture stop STO and the image plane IMA are not located... Figure 15 As shown in the image.

[0131] like Figure 15 As shown, the optical imaging system may include a lens barrel P0 and an imaging assembly and a second spacer element P2 assembled within the lens barrel P0. The imaging assembly includes a linear polarizing film LP, a reflective polarizing element RP, a quarter-wave plate QWP, a first lens E1, a second lens E2, a third lens E3, a fourth lens E4, and a partially reflective layer BS, arranged sequentially along the optical axis from the first side to the second side. An aperture stop STO is positioned between the first side and the linear polarizing film LP (e.g., ...). Figure 2 ).

[0132] The first lens E1 has positive optical power, with its first side surface S1 being planar and its second side surface S2 being concave. The second lens E2 has negative optical power, with its first side surface S3 being concave and its second side surface S4 being convex. The third lens E3 has negative optical power, with its first side surface S5 being convex and its second side surface S6 being concave. The fourth lens E4 has positive optical power, with its first side surface S7 being convex and its second side surface S8 being convex. A linear polarizing film LP, a reflective polarizing element RP, and a quarter-wave plate QWP are attached to the first side surface S1 of the first lens E1. A partially reflective layer BS is attached to the second side surface S8 of the fourth lens E4.

[0133] In this example, an image plane IMA can be provided on the second side of the optical imaging system. The image plane IMA can, for example, be a display screen. Light from the image plane IMA passes sequentially through a fourth lens E4, a third lens E3, a second lens E2, a first lens E1, and a quarter-wave plate QWP, reaching a reflective polarizing element RP, where it is reflected to form the first reflected image light. The first reflected image light passes sequentially through the quarter-wave plate QWP, the first lens E1, the second lens E2, the third lens E3, and the fourth lens E4, reaching a partial reflective layer BS on the second side of the fourth lens, where it is reflected to form the second reflected image light. The second reflected image light passes sequentially through the fourth lens E4, the third lens E3, the second lens E2, the first lens E1, the quarter-wave plate QWP, the reflective polarizing element RP, and the linear polarizing film LP to the aperture stop STO and is finally projected onto the human eye. For example, the light from this optical imaging system, after two reflections, is finally projected onto the human eye.

[0134] Table 7 shows the basic parameters of the optical imaging system of Example 7, where the units for radius of curvature and thickness / distance are millimeters (mm).

[0135]

[0136] Table 7

[0137] In this embodiment, the effective focal length f2 of the second lens is -108.19mm, and the combined focal length f34 of the third and fourth lenses is 121.26mm.

[0138] The object side and image side of any one of the first side surface S3 and the second side surface S4 of the second lens E2 and the first side surface S7 of the fourth lens E4 are aspherical surfaces. Table 8 gives the conic coefficient k and higher-order coefficients A4, A6, A8, A10, A12 and A14 that can be used for each aspherical surface S2-S8 in Example 7.

[0139] Face number k A4 A6 A8 A10 A12 A14 S2 / S3 0.7257 5.62E-05 -4.53E-07 5.96E-10 3.15E-12 -6.16E-15 0.00E+00 S4 41.4690 7.82E-06 -7.88E-08 2.61E-10 7.82E-14 -2.42E-16 -5.28E-19 S5 -77.9981 -6.13E-06 -7.20E-09 1.71E-10 -3.12E-13 0.00E+00 0.00E+00 S6 / S7 -95.7107 6.09E-06 -1.00E-07 1.78E-10 0.00E+00 0.00E+00 0.00E+00 S8 -29.8556 -7.89E-06 9.21E-09 3.55E-11 -9.09E-14 0.00E+00 0.00E+00

[0140] Table 8

[0141] Example 8

[0142] The following is for reference Figure 2 and Figure 16 Describes an optical imaging system according to Embodiment 8 of this application. In this system, the aperture stop STO and the image plane IMA are not located... Figure 16 As shown in the image.

[0143] like Figure 16As shown, the optical imaging system may include a lens barrel P0 and an imaging assembly and a second spacer element P2 assembled within the lens barrel P0. The imaging assembly includes a linear polarizing film LP, a reflective polarizing element RP, a quarter-wave plate QWP, a first lens E1, a second lens E2, a third lens E3, a fourth lens E4, and a partially reflective layer BS, arranged sequentially along the optical axis from the first side to the second side. An aperture stop STO is positioned between the first side and the linear polarizing film LP (e.g., ...). Figure 2 ).

[0144] The structure of the imaging group in this embodiment is the same as that in Embodiment 7. That is, the basic parameter table of the optical imaging system in this embodiment is the same as that in Table 7, and the aspherical coefficient table is the same as that in Table 8. The difference between this embodiment and Embodiment 7 lies in the structural dimensions and other parameters of the lens barrel P0 and the second spacer element P2. The values ​​of multiple parameters of the lens barrel P0 and the second spacer element P2 included in the optical imaging systems of this embodiment and Embodiment 7 are shown in Table 9 below.

[0145] Example 9

[0146] The following is for reference Figure 2 and Figure 17 Describes an optical imaging system according to Embodiment 9 of this application. In this system, the aperture stop STO and the image plane IMA are not located... Figure 17 As shown in the image.

[0147] like Figure 17 As shown, the optical imaging system may include a lens barrel P0 and an imaging assembly and a second spacer element P2 assembled within the lens barrel P0. The imaging assembly includes a linear polarizing film LP, a reflective polarizing element RP, a quarter-wave plate QWP, a first lens E1, a second lens E2, a third lens E3, a fourth lens E4, and a partially reflective layer BS, arranged sequentially along the optical axis from the first side to the second side. An aperture stop STO is positioned between the first side and the linear polarizing film LP (e.g., ...). Figure 2 ).

[0148] The structure of the imaging group in this embodiment is the same as that in Embodiment 7. That is, the basic parameter table of the optical imaging system in this embodiment is the same as that in Table 7, and the aspherical coefficient table is the same as that in Table 8. The difference between this embodiment and Embodiment 7 lies in the structural dimensions and other parameters of the lens barrel P0 and the second spacer element P2. The values ​​of multiple parameters of the lens barrel P0 and the second spacer element P2 included in the optical imaging systems of this embodiment and Embodiment 7 are shown in Table 9 below.

[0149] Figure 18 The on-axis chromatic aberration curves of the optical imaging systems of Examples 7, 8 and 9 are shown, which represent the deflection of the focal point after light of different wavelengths passes through the optical imaging system. Figure 19Astigmatism curves of the optical imaging systems of Examples 7, 8, and 9 are shown, representing the meridional and sagittal image plane curvatures corresponding to different half-field angles. Figure 20 The distortion curves of the optical imaging systems of Examples 7, 8, and 9 are shown, representing the distortion magnitude values ​​corresponding to different half-field angles. According to... Figures 18 to 20 It can be seen that the optical imaging systems given in Examples 7, 8 and 9 can achieve good imaging quality.

[0150] Table 9 shows the values ​​of parameters d2s, d2m, D2s, D2m, d0m, D0m, EP02, CP2, and L for each embodiment in Examples 1-9. At least some of these parameters can be measured using the annotation method shown in the figures, and the units for all parameters listed in Table 9 are mm.

[0151] Parameters\Example 1 2 3 4 5 6 7 8 9 d2s 35.196 39.009 37.587 37.726 38.499 37.726 39.151 39.151 38.574 d2m 41.042 41.042 40.882 41.601 41.010 41.284 41.038 41.038 41.038 D2s 41.060 40.731 41.060 41.532 41.532 41.532 43.108 43.108 42.230 D2m 41.788 41.788 41.629 43.010 43.010 42.827 43.285 43.285 42.835 d0m 45.295 45.296 45.089 46.045 46.043 46.041 45.507 45.506 45.503 D0m 47.586 47.586 47.147 48.332 48.332 48.332 47.797 47.797 47.797 EP02 6.105 5.518 6.105 7.502 7.502 7.502 6.847 6.847 6.847 CP2 3.454 3.822 3.454 2.675 2.675 2.675 2.903 2.903 2.903 L 14.090 13.871 13.140 13.618 13.033 13.618 14.849 13.911 14.849

[0152] Table 9

[0153] Table 10 shows the values ​​of the conditional expressions for each of the embodiments in Examples 1-9.

[0154] Conditional / Example 1 2 3 4 5 6 7 8 9 (CP2+EP02) / T23 4.57 4.46 4.57 6.78 6.78 6.78 7.72 7.72 7.72 R4 / (D2s×N2) -2.07 -2.09 -2.07 -2.78 -2.78 -2.78 -1.80 -1.80 -1.83 D0m-D2m 5.80 5.80 5.52 5.32 5.32 5.51 4.51 4.51 4.96 (CT3+CT4) / (L-EP02) 0.75 0.72 0.85 1.26 1.40 1.26 0.83 0.94 0.83 (d2m-d2s) / T23 2.79 0.97 1.57 2.58 1.67 2.37 1.49 1.49 1.95 R5 / d2m 4.45 4.45 4.47 5.38 5.45 5.42 4.45 4.45 4.45 f2 / EP02 -19.42 -21.49 -19.42 -25.74 -25.74 -25.74 -15.80 -15.80 -15.80 R2 / d2s -1.37 -1.24 -1.29 -2.00 -1.96 -2.00 -1.15 -1.15 -1.17 R6 / d0m 0.88 0.88 0.88 1.24 1.24 1.24 1.27 1.27 1.27 L / (CT1+CT2) 3.13 3.08 2.92 3.89 3.72 3.89 2.70 2.53 2.70 f34 / D0m 2.67 2.67 2.69 1.57 1.57 1.57 2.54 2.54 2.54

[0155] Table 10

[0156] This application also provides an optical device, which can be a standalone projection device such as a projector, or a projection module integrated into a mobile electronic device such as a virtual reality device. This optical device is equipped with the optical imaging system described above.

[0157] The above description is merely a preferred embodiment of this application and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of this application is not limited to technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the application's concept. For example, technical solutions formed by substituting the above-described features with (but not limited to) technical features with similar functions disclosed in this application.

Claims

1. An optical imaging system, characterized in that, include: The imaging assembly, along the optical axis from the first side to the second side, sequentially includes a linear polarizing film, a reflective polarizing element, a quarter-wave plate, a first lens, a second lens, a third lens, a fourth lens, and a partially reflective layer; wherein the first lens and the second lens are cemented together, and the third lens and the fourth lens are cemented together. The first lens has positive or negative optical power, its first side surface is concave or flat, and its second side surface is convex. The second lens has negative optical power, and its second side surface is convex. The third lens has negative optical power, and its first side surface is convex and its second side surface is concave. The fourth lens has positive optical power, and its first side surface is convex, and its second side surface is convex. A second spacer element is disposed on and in contact with the second side surface of the second lens; and The imaging group and the second spacer element are placed inside the lens barrel; The optical imaging system has four lenses with optical power. Wherein, the linear polarizing film is attached to the first side of the reflective polarizing element, the reflective polarizing element is attached to the first side of the quarter-wave plate, the quarter-wave plate is attached to the first side of the first lens, and the partial reflective layer is attached to the second side of the fourth lens. The outer diameter D0m of the second side end face of the lens barrel and the outer diameter D2m of the second side face of the second spacer element satisfy: 4.51mm≤D0m-D2m≤5.80mm; The inner diameter d2m of the second side of the second spacer element, the inner diameter d2s of the first side of the second spacer element, and the axial distance T23 from the second side of the second lens to the first side of the third lens satisfy: 0.97≤(d2m-d2s) / T23≤2.79; The first side is the human eye side, and the second side is the display screen side.

2. The optical imaging system according to claim 1, characterized in that, The radius of curvature R4 of the second side surface of the second lens, the outer diameter D2s of the first side surface of the second spacer element and the refractive index N2 of the second lens satisfy: -2.78≤R4 / (D2s×N2)≤-1.

80.

3. The optical imaging system according to claim 1, characterized in that, The maximum thickness CP2 of the second spacer element, the distance EP02 between the first side end face of the lens barrel and the second spacer element along the optical axis, and the axial distance T23 between the second side face of the second lens and the first side face of the third lens satisfy: 4.46≤(CP2+EP02) / T23≤7.

72.

4. The optical imaging system according to claim 1, characterized in that, The center thickness CT3 of the third lens on the optical axis, the center thickness CT4 of the fourth lens on the optical axis, the distance L between the first side end face and the second side end face of the lens barrel along the optical axis and the distance EP02 between the first side end face and the second spacer element along the optical axis satisfy: 0.72≤(CT3+CT4) / (L-EP02)≤1.

40.

5. The optical imaging system according to claim 1, characterized in that, The radius of curvature R5 of the first side of the third lens and the inner diameter d2m of the second side of the second spacer element satisfy: 4.45≤R5 / d2m≤5.

45.

6. The optical imaging system according to claim 1, characterized in that, The effective focal length f2 of the second lens and the distance EP02 between the first side end face of the lens barrel and the second spacer element along the optical axis satisfy: -25.74≤f2 / EP02≤-15.

80.

7. The optical imaging system according to claim 1, characterized in that, The radius of curvature R2 of the second side surface of the first lens and the inner diameter d2s of the first side surface of the second spacer element satisfy: -2.00≤R2 / d2s≤-1.

15.

8. The optical imaging system according to any one of claims 1 to 7, characterized in that, The radius of curvature R6 of the second side surface of the third lens and the inner diameter d0m of the second side end face of the lens barrel satisfy the following condition: 0.88≤R6 / d0m≤1.

27.

9. The optical imaging system according to any one of claims 1 to 7, characterized in that, The distance L between the first and second end faces of the lens barrel along the optical axis, the center thickness CT1 of the first lens on the optical axis, and the center thickness CT2 of the second lens on the optical axis satisfy the following: 2.53≤L / (CT1+CT2)≤3.

89.

10. The optical imaging system according to any one of claims 1 to 7, characterized in that, The combined focal length f34 of the third lens and the fourth lens satisfies the following condition with respect to the outer diameter D0m of the second side end face of the lens barrel: 1.57≤f34 / D0m≤2.69.

Images