A projection lens and projection device

Abstract

This application provides a projection lens and a projection device, belonging to the field of display technology, aiming to improve the projection optical effect. The projection lens includes: a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, and a seventh lens arranged sequentially with their optical axes coincident from the image side to the object side along the opposite direction of light transmission; wherein, the image side is the side of the projection lens closer to the projection imaging surface, and the object side is the side of the projection lens closer to the original image being projected; wherein, the first lens, the second lens, and the third lens are all convex-concave lenses, with the image side being convex and the object side being concave; the fourth lens is a biconvex lens; the fifth lens is a concave-convex lens, with the image side being concave and the object side being convex; the sixth lens is a biconcave lens; and the seventh lens is a concave-convex lens, with the image side being concave and the object side being convex.

Description

Technical Field

[0001] This application belongs to the field of display technology, specifically relating to a projection lens and a projection device. Background Technology

[0002] In recent years, liquid crystal display (LCD) projection technology has matured and manufacturing processes have improved, giving LCD projectors advantages such as high backlight efficiency, high optical engine heat dissipation performance, small LCD chip size, and high resolution. LCD projectors are low-cost and have high sales volume, and are currently widely used in various aspects of life.

[0003] However, current LCD projectors generally use no-offset, low-offset, or physical-offset methods. In the case of 100% offset, the cropping of the image can easily lead to a loss of optical performance parameters (brightness, sharpness) of the projector, affecting the quality of the projected image. Utility Model Content

[0004] This application provides a projection lens and a projection device for improving projection optical effects.

[0005] A first aspect of this application provides a projection lens, the lens comprising at least:

[0006] A first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, and a seventh lens are arranged sequentially with their optical axes overlapping, from the image side to the object side along the opposite direction of light transmission; wherein, the image side is the side of the projection lens closest to the projection imaging surface, and the object side is the side of the projection lens closest to the original image being projected.

[0007] The first lens, the second lens, and the third lens are all convex-concave lenses, with the image side being convex and the object side being concave.

[0008] The fourth lens is a biconvex lens;

[0009] The fifth lens is a concave-convex lens, with the image side being concave and the object side being convex.

[0010] The sixth lens is a biconcave lens;

[0011] The seventh lens is a concave-convex lens, with the image side being concave and the object side being convex.

[0012] A second aspect of this application provides a projection lens, the lens comprising at least:

[0013] A first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, and a seventh lens are arranged sequentially with their optical axes overlapping, from the image side to the object side along the opposite direction of light transmission; wherein, the image side is the side of the projection lens closest to the projection imaging surface, and the object side is the side of the projection lens closest to the original image being projected.

[0014] The optical power matching relationship between the first lens, the second lens, and the third lens is as follows: the first lens has negative optical power, the second lens has positive optical power, and the third lens has negative optical power.

[0015] In one possible implementation, the optical power matching relationship between the fourth lens, the fifth lens, the sixth lens, and the seventh lens is as follows: the fourth lens has positive optical power, the fifth lens has positive optical power, the sixth lens has negative optical power, and the seventh lens has positive optical power.

[0016] A third aspect of this application also provides a projection device, the device comprising:

[0017] The projection lens described in the first or second aspect of the embodiments of this application;

[0018] The display module emits light into the projection lens and exits from the projection lens.

[0019] In one possible implementation, the device further includes:

[0020] A Fresnel lens is disposed with its optical axis aligned with that of the projection lens, and the Fresnel lens is located between the display module and the projection lens;

[0021] The plane containing the Fresnel lens is parallel to the plane containing the display module. One side of the display module is aligned with the optical axis of the Fresnel lens, and the light emission direction of the display module is parallel to the extension direction of the optical axis of the projection lens.

[0022] In one possible implementation, the air gap between the projection lens and the Fresnel lens is greater than or equal to 65.72 mm and less than or equal to 66.88 mm; the air gap between the Fresnel lens and the display module is greater than or equal to 10.74 mm and less than or equal to 12.00 mm.

[0023] In one possible implementation, the light emission direction of the display module is perpendicular to the optical axis extension direction of the projection lens, and the device further includes:

[0024] Fresnel lenses and mirrors;

[0025] The plane containing the Fresnel lens is parallel to the plane containing the display module. The Fresnel lens is located between the display module and the reflector. The reflector is used to reflect the light from the display module that has passed through the Fresnel lens to the projection lens.

[0026] One side of the display module is aligned with the optical axis of the Fresnel lens, and the light emission direction of the display module is parallel to the extension direction of the optical axis of the Fresnel lens.

[0027] The beneficial effects of this application are as follows: the projection lens and projection device proposed in the embodiments of this application can achieve excellent imaging performance through optical design. In particular, when achieving 100% optical off-axis projection, it can reduce the loss of optical brightness and resolution after keystone correction, improve the projection optical effect, and enhance the comfort of viewing.

[0028] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments or related technologies of this application, the accompanying drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. It should be noted that the scale in the drawings is for illustration only and does not represent the actual scale.

[0030] Figure 1 This is a schematic diagram of an off-axis projection imaging effect in an embodiment of this application;

[0031] Figure 2 This is a schematic diagram of a 100% off-axis projection imaging effect in an embodiment of this application;

[0032] Figure 3 This is a schematic diagram of the structure of a projection lens in an embodiment of this application;

[0033] Figure 4 This is a schematic diagram of a projection device structure for 100% optical off-axis projection according to an embodiment of this application;

[0034] Figure 5 This is a comparison diagram of the field of view radii of off-axis imaging and off-axis imaging in an embodiment of this application;

[0035] Figure 6This is a schematic diagram of the main ray propagation in a Zemax imaging embodiment of this application;

[0036] Figure 7 This is a schematic diagram of the MTF of a projection lens in an embodiment of this application;

[0037] Figure 8 This is a field curvature diagram and a relative distortion diagram of a projection lens in an embodiment of this application;

[0038] Figure 9 This is a schematic diagram of TV distortion of a projection lens in an embodiment of this application;

[0039] Figure 10 This is a chromatic aberration diagram of a projection lens in an embodiment of this application;

[0040] Figure 11 This is a relative illumination diagram of a projection lens in an embodiment of this application;

[0041] Figure 12 This is a schematic diagram of another projection device in an embodiment of this application. Detailed Implementation

[0042] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0043] The terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and not to describe a specific order or sequence. It should be understood that such terms can be used interchangeably where appropriate so that embodiments of this application can be implemented in orders other than those illustrated or described herein, and the objects distinguished by "first" and "second" are generally of the same class, not limited in number; for example, the first object can be one or at least two. Furthermore, in the specification and claims, "and / or" indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0044] In recent years, LCD chip projection technology has seen significant improvements in three main areas: 1. Mature LCD technology and improved manufacturing processes enable the production of small-sized, high-resolution LCD chips, such as 2.69-inch FHD, 3.0-inch FHD, 4.45-inch FHD, and 5.0-inch UHD; 2. Improved backlight efficiency, achieved through flip-chip LED light source packaging, enhances projection backlight output and ensures sufficient luminous flux. Currently, projectors using LCD technology can achieve brightness exceeding CIVA 600lm, comparable to mainstream DLP projection products; 3. Enhanced heat dissipation in the optical engine system and the use of more heat-resistant film materials provide higher performance limits for LCD projectors. LCDs are currently domestically developed and manufactured, boasting low cost and high sales volume, and are widely used in various aspects of daily life. LCD projection is gradually gaining a significant market share in competition with Digital Light Processing (DLP) projection. DLP projectors typically have 100% optical off-axis design for their imaging lenses. Their key feature is that the projected image is above the horizontal axis of the projection lens by default, which prevents the projected image from shining onto the table.

[0045] Currently, LCD lenses generally employ off-axis, low-off-axis, or physical off-axis designs. When projecting onto a desktop, lenses with off-axis or low-off-axis designs require avoiding interference from other objects, typically necessitating raising the projector or using a gimbal to achieve a certain tilt angle. Raising the projector requires additional specialized equipment, and the tilt angle of the projected image results in trapezoidal distortion, compromising both optical brightness and sharpness after correction. Physical off-axis lenses, on the other hand, adjust the light angle by tilting the optical components during design, essentially sacrificing optical image quality to achieve the off-axis effect. Therefore, achieving off-axis projection in current LCD projectors always sacrifices some projection performance parameters, such as brightness and resolution loss.

[0046] Reference Figure 1 , Figure 1 A schematic diagram of an off-axis projection imaging effect is shown, such as... Figure 1 As shown, when projecting onto a desktop using a non-offset lens, some light is blocked, preventing the complete content from being displayed on the screen. Therefore, it's generally necessary to raise the projector to a certain angle or use a tripod to ensure the image is projected entirely onto the screen. (See reference...) Figure 2 , Figure 2 A schematic diagram of a 100% off-axis projection imaging effect is shown, such as... Figure 2 As shown, a 100% off-axis lens can project an image onto a screen above the table level under the same conditions without any lifting or gimbal.

[0047] In view of the above problems, this application provides a projection lens and projection device that can achieve excellent imaging performance through optical design. In particular, when achieving 100% optical off-axis projection, it can reduce the loss of optical brightness and resolution after keystone correction, improve the projection optical effect, and enhance the viewing comfort.

[0048] The first aspect of this application discloses a projection lens, referring to... Figure 3 , Figure 3 A schematic diagram of a projection lens structure is shown, such as... Figure 3 As shown, the lens includes at least:

[0049] A first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, and a seventh lens are arranged sequentially with their optical axes overlapping, from the image side to the object side along the opposite direction of light transmission; wherein, the image side is the side of the projection lens closest to the projection imaging surface, and the object side is the side of the projection lens closest to the original image being projected.

[0050] The first lens, the second lens, and the third lens are all convex-concave lenses, with the image side being convex and the object side being concave.

[0051] The fourth lens is a biconvex lens;

[0052] The fifth lens is a concave-convex lens, with the image side being concave and the object side being convex.

[0053] The sixth lens is a biconcave lens;

[0054] The seventh lens is a concave-convex lens, with the image side being concave and the object side being convex.

[0055] Specifically, the projection lens proposed in this embodiment is located on the light-emitting side of the (liquid crystal) display module. The projection lens includes a magnifying side and a reducing side. The reducing side is the side of the projection lens closer to the display module, and the magnifying side is the side of the projection lens farther away from the display module. Figure 3 As shown, the projection lens includes: optical axes arranged sequentially from the magnification side to the reduction side in the opposite direction of light transmission (from the magnification side to the reduction side). Figure 3 The first lens G01, the second lens G02, the third lens G03, the fourth lens G04, the fifth lens G05, the sixth lens G06, and the seventh lens G07 are set to overlap (the dashed lines in the image).

[0056] The projection lens proposed in this embodiment is a projection lens suitable for LCD projection imaging optical systems. To improve the optical effect of the projection lens, it is modified into a lens composed of seven lenses. In this embodiment, the image-side surface is convex, and the reduction-side surface is concave. The image-side surface is the projection imaging side (light emanating side), i.e., the surface containing the magnification side; the object-side surface is the side containing the display module (light incident side), i.e., the surface containing the reduction side. The light emitted from the display module enters the projection lens and exits from it in the following order: seventh lens G07, sixth lens G06, fifth lens G05, fourth lens G04, third lens G03, second lens G02, and first lens G01. The optical axes of these lenses coincide, meaning that the optical axes of each lens extend in the same direction. The projection lens, composed of at least these seven lenses, has advantages such as high resolution, high uniformity, and high light utilization, which can improve the edge sharpness of the projected image and enhance the projection imaging quality. Furthermore, the structural parameters of each lens in the projection lens can be adjusted to achieve the desired imaging quality.

[0057] In one possible implementation, the optical power matching relationship between the first lens, the second lens, and the third lens is as follows: the first lens has negative optical power, the second lens has positive optical power, and the third lens has negative optical power.

[0058] In one possible implementation, the optical power matching relationship between the fourth lens, the fifth lens, the sixth lens, and the seventh lens is as follows: the fourth lens has positive optical power, the fifth lens has positive optical power, the sixth lens has negative optical power, and the seventh lens has positive optical power.

[0059] In one possible implementation, the radius of curvature of the image side of the first lens is greater than the radius of curvature of the object side of the first lens.

[0060] The radius of curvature of the image side of the second lens is smaller than the radius of curvature of the object side of the second lens;

[0061] The radius of curvature of the image side of the third lens is greater than the radius of curvature of the object side of the third lens.

[0062] The radius of curvature of the image side of the fourth lens is smaller than the radius of curvature of the object side of the fourth lens.

[0063] The radius of curvature of the image side of the fifth lens is greater than the radius of curvature of the object side of the fifth lens;

[0064] The radius of curvature of the image side of the sixth lens is smaller than the radius of curvature of the object side of the sixth lens.

[0065] The radius of curvature of the image side of the seventh lens is greater than the radius of curvature of the object side of the seventh lens.

[0066] In one possible implementation, the curvature along the light emission direction is positive and the curvature in the opposite direction is negative. The radius of curvature of the image side of the first lens is greater than or equal to 41.5 mm and less than or equal to 42.6 mm; the radius of curvature of the object side is greater than or equal to 27.4 mm and less than or equal to 28.5 mm.

[0067] The radius of curvature of the image side of the second lens is greater than or equal to 41.8 mm and less than or equal to 42.9 mm; the radius of curvature of the object side is greater than or equal to 95.1 mm and less than or equal to 96.2 mm.

[0068] The radius of curvature of the image side of the third lens is greater than or equal to 109.9 mm and less than or equal to 111.0 mm; the radius of curvature of the object side is greater than or equal to 32.9 mm and less than or equal to 34.0 mm.

[0069] The radius of curvature of the image side of the fourth lens is greater than or equal to 65.4 mm and less than or equal to 66.5 mm; the radius of curvature of the object side is greater than or equal to -146.7 mm and less than or equal to -144.6 mm.

[0070] The radius of curvature of the image side of the fifth lens is greater than or equal to -2856.7 mm and less than or equal to -2854.6 mm; the radius of curvature of the object side is greater than or equal to -43.6 mm and less than or equal to -41.5 mm.

[0071] The radius of curvature of the image side of the sixth lens is greater than or equal to -54.9 mm and less than or equal to -53.8 mm; the radius of curvature of the object side is greater than or equal to 74.3 mm and less than or equal to 75.4 mm.

[0072] The radius of curvature of the image side of the seventh lens is greater than or equal to -204.6 mm and less than or equal to -203.5 mm; the radius of curvature of the object side is greater than or equal to -67.2 mm and less than or equal to -66.1 mm.

[0073] In one possible implementation, the center thickness of the first lens is less than the center thickness of the third lens, and the center thickness of the third lens is less than the center thickness of the second lens; wherein, the center thickness is the thickness of the lens at its center along the optical axis.

[0074] The center thickness of the sixth lens is less than the center thickness of the seventh lens, the center thickness of the seventh lens is less than the center thickness of the fifth lens, and the center thickness of the fifth lens is less than the center thickness of the fourth lens;

[0075] The center thickness of the fourth lens is greater than the center thickness of the third lens, but less than the center thickness of the second lens.

[0076] Specifically, center thickness refers to the thickness of the lens along the optical axis at the center point of the lens. In projection lens design, the center thickness (CT) of each lens has a significant impact on the overall optical imaging effect of the lens, mainly reflected in aberration correction, optical path control, and system compactness. The center thickness of the lens not only affects the focal length of the lens itself, but also affects the propagation path of light within the lens. Optimizing the thickness can reduce higher-order aberrations. Optionally, the center thickness of the first lens is greater than or equal to 1.75 mm and less than or equal to 1.95 mm; the center thickness of the second lens is greater than or equal to 7.66 mm and less than or equal to 7.91 mm; the center thickness of the third lens is greater than or equal to 4.85 mm and less than or equal to 5.03 mm; the center thickness of the fourth lens is greater than or equal to 7.15 mm and less than or equal to 7.33 mm; the center thickness of the fifth lens is greater than or equal to 6.56 mm and less than or equal to 6.72 mm; the center thickness of the sixth lens is greater than or equal to 1.81 mm and less than or equal to 1.97 mm; and the center thickness of the seventh lens is greater than or equal to 4.84 mm and less than or equal to 5.06 mm.

[0077] In one possible implementation, the refractive index of the first lens is less than the refractive index of the third lens, and the refractive index of the third lens is less than the refractive index of the second lens.

[0078] The refractive index of the fifth lens is less than that of the sixth lens, and the refractive index of the sixth lens is less than that of the fourth lens or the seventh lens;

[0079] The refractive index of the fifth lens is less than that of the third lens.

[0080] Specifically, refractive index represents the angle of refraction when light passes through a lens. The refractive index (RI) of a lens has a decisive influence on the imaging effect of the lens, directly related to the lens's optical path control, aberration correction, system size, and performance limits. Optionally, the refractive index of the first lens is greater than or equal to 1.51 and less than or equal to 1.57; the refractive index of the second lens is greater than or equal to 1.79 and less than or equal to 1.81; the refractive index of the third lens is greater than or equal to 1.60 and less than or equal to 1.64; the refractive index of the fourth lens is greater than or equal to 1.79 and less than or equal to 1.81; the refractive index of the fifth lens is greater than or equal to 1.51 and less than or equal to 1.57; the refractive index of the sixth lens is greater than or equal to 1.65 and less than or equal to 1.68; and the refractive index of the seventh lens is greater than or equal to 1.79 and less than or equal to 1.81.

[0081] In one possible implementation, the dispersion coefficient of the third lens is smaller than that of the second lens, and the dispersion coefficient of the second lens is smaller than that of the first lens.

[0082] The dispersion coefficient of the sixth lens is less than that of the fourth lens or the seventh lens, and the dispersion coefficient of the fourth lens or the seventh lens is less than that of the fifth lens.

[0083] The dispersion coefficient of the sixth lens is smaller than that of the third lens.

[0084] Specifically, in optical lens design, the dispersion coefficient (Abbe number, V) d The dispersion coefficient (CFC) is a key parameter for measuring the dispersion characteristics of lens materials. It quantifies the degree of dispersion of light of different colors (wavelengths) by the lens, i.e., the characteristic of the refractive index changing with wavelength, and has a direct impact on the overall imaging effect of the lens (especially chromatic aberration correction). Optionally, the dispersion coefficient of the first lens is greater than or equal to 63.1 and less than or equal to 66.2; the dispersion coefficient of the second lens is greater than or equal to 45.5 and less than or equal to 48.6; the dispersion coefficient of the third lens is greater than or equal to 34.8 and less than or equal to 36.4; the dispersion coefficient of the fourth lens is greater than or equal to 45.5 and less than or equal to 48.6; the dispersion coefficient of the fifth lens is greater than or equal to 63.1 and less than or equal to 66.2; the dispersion coefficient of the sixth lens is greater than or equal to 31.2 and less than or equal to 34.3; and the dispersion coefficient of the seventh lens is greater than or equal to 45.5 and less than or equal to 48.6.

[0085] In one possible implementation, the second lens, the fourth lens, and the seventh lens have the same refractive index and the same dispersion coefficient.

[0086] In this embodiment, the second lens G02, the fourth lens G04, and the seventh lens G07 exhibit similar or identical optical material properties in actual processes. They can be made using the same glass material (i.e., glass materials with the same refractive index and dispersion coefficient) and still meet the performance requirements of this application. In this embodiment, using the same glass material to fabricate multiple lenses further simplifies the process and reduces the production cost of the lenses.

[0087] In one possible implementation, the focal length ratio of the first lens to the second lens is greater than or equal to -2.2 and less than or equal to -2.1.

[0088] The focal length ratio of the third lens to the second lens is greater than or equal to -1.1 and less than or equal to -1.0.

[0089] The focal length ratio between the fourth lens and the sixth lens is greater than or equal to -1.4 and less than or equal to -1.3.

[0090] The focal length ratio of the fifth lens to the sixth lens is greater than or equal to -2.2 and less than or equal to -2.1;

[0091] The focal length ratio of the seventh lens to the sixth lens is greater than or equal to -2.2 and less than or equal to -2.1.

[0092] Specifically, the sign of the lens focal length is used to distinguish the type of lens (convex or concave) and its optical characteristics (converging or diverging light rays). A positive focal length (f>0) indicates that the lens is a convex lens (converging lens), which can converge parallel light rays to the focal point. A negative focal length (f<0) indicates that the lens is a concave lens (diverging lens), which causes parallel light rays to diverge, and their backward extensions intersect at the virtual focal point.

[0093] Optionally, the focal length ratio of the first lens to the second lens is -2.112:1; the focal length ratio of the third lens to the second lens is -1.047:1; the focal length ratio of the fourth lens to the sixth lens is -1.396:1; the focal length ratio of the fifth lens to the sixth lens is -2.161:1; and the focal length ratio of the seventh lens to the sixth lens is -2.135:1.

[0094] In one possible implementation, the lens further includes an aperture stop located between the third lens and the fourth lens. Specifically, an aperture stop is a physical element in an optical system used to limit the width of a light beam, i.e., to limit the diameter of the light beam passing through the optical system, thus determining the effective aperture for imaging. The aperture stop directly controls the amount of light entering the system and affects the brightness, depth of field, resolution, and aberrations of the image. Figure 3As shown, the aperture stop STOP is located between the third lens G03 and the fourth lens G04, and the central optical axis of the aperture stop coincides with the optical axis of the lens. Optionally, the aperture of the aperture stop is greater than or equal to 26.8 mm and less than or equal to 27.5 mm.

[0095] The air gap between the first lens and the second lens is greater than the air gap between the second lens and the third lens;

[0096] The air gap between the second lens and the third lens is greater than the air gap between the third lens and the aperture stop;

[0097] The air gap between the third lens and the aperture stop is greater than the air gap between the sixth lens and the seventh lens;

[0098] The air gap between the sixth lens and the seventh lens is greater than the air gap between the fourth lens and the fifth lens;

[0099] The air gap between the fourth lens and the fifth lens is greater than the air gap between the aperture stop and the fourth lens; and the air gap between the fourth lens and the fifth lens is greater than the air gap between the fifth lens and the sixth lens.

[0100] Specifically, the air gap between lenses refers to the physical distance (air layer thickness) between the surfaces of two adjacent lenses, usually measured in millimeters (mm). The air gap alters the propagation path of light, affecting optical power distribution and aberration balance. Optionally, the air gap between the first lens and the second lens is greater than or equal to 16.31 mm and less than or equal to 17.42 mm; the air gap between the second lens and the third lens is greater than or equal to 7.34 mm and less than or equal to 8.55 mm; the air gap between the third lens and the aperture stop is greater than or equal to 4.88 mm and less than or equal to 5.14 mm; the air gap between the aperture stop and the fourth lens is greater than or equal to 0.75 mm and less than or equal to 0.93 mm; the air gap between the fourth lens and the fifth lens is greater than or equal to 1.21 mm and less than or equal to 1.45 mm; the air gap between the fifth lens and the sixth lens is greater than or equal to 0.78 mm and less than or equal to 0.96 mm; and the air gap between the sixth lens and the seventh lens is greater than or equal to 4.41 mm and less than or equal to 4.75 mm.

[0101] In one possible implementation, the aperture of the first lens is larger than the aperture of the second lens;

[0102] The aperture of the second lens is larger than that of the seventh lens;

[0103] The aperture of the seventh lens is larger than that of the sixth lens;

[0104] The aperture of the sixth lens is larger than that of the third lens;

[0105] The aperture of the third lens is larger than that of the fifth lens;

[0106] The aperture of the fifth lens is larger than that of the fourth lens.

[0107] The aperture of a lens refers to the effective area on the lens actually used for light transmission (i.e., the maximum diameter range of the lens surface that allows light to pass through). It is typically slightly smaller than the physical diameter of the lens; light exceeding this area will be blocked by the frame, lens barrel, or coating boundary. Optionally, the aperture of the first lens is greater than or equal to 61.0 mm and less than or equal to 62.0 mm; the aperture of the second lens is greater than or equal to 49.0 mm and less than or equal to 49.5 mm; the aperture of the third lens is greater than or equal to 40.0 mm and less than or equal to 41.0 mm; the aperture of the fourth lens is greater than or equal to 35.5 mm and less than or equal to 36.2 mm; the aperture of the fifth lens is greater than or equal to 38.2 mm and less than or equal to 39.4 mm; the aperture of the sixth lens is greater than or equal to 44.0 mm and less than or equal to 44.8 mm; and the aperture of the seventh lens is greater than or equal to 46.1 mm and less than or equal to 47.3 mm.

[0108] The projection lens proposed in this application embodiment achieves excellent imaging performance through optical design. Especially when achieving 100% optical off-axis projection, it reduces the loss of optical brightness and resolution after keystone correction, improves projection optical effects, and enhances viewing comfort. Specifically, refer to... Figure 4 , Figure 4 A schematic diagram of a projection device with 100% optical off-axis projection is shown, as follows: Figure 4 As shown, the projection device includes a projection lens and a display module, allowing light emitted from the display module to enter the projection lens (the reduced side) and exit from the projection lens (the magnified side). Figure 4 As shown, light emitted from one side of the display module passes through the center of the Fresnel lens, enters the projection lens, and exits along the optical axis of the projection lens. Light emitted from the other side of the display module passes through the Fresnel lens, enters the projection lens, and exits as... Figure 4 The principal ray of the maximum imaging field of view is emitted.

[0109] Reference Figure 5 , Figure 5 A comparison diagram of the field of view radii for off-axis and off-axis imaging is shown, in which... Figure 5 In this context, (a) represents the field of view radius for off-axis imaging. Figure 5 In the diagram, (b) represents the field of view radius for off-axis imaging. For example... Figure 5 As shown in (a), for a lens with off-axis imaging, the position of its central axis (i.e., the direction of the lens's optical axis) will coincide with the position of the center point of the display module (such as an LCD chip). Correspondingly, in optical design, the radius of the maximum field of view circle (field radius) will be smaller. An example is... Figure 5 As shown in (a), when the LCD chip is 3.0 inches in size, the field of view radius Y0 = 38.1 mm. Figure 5 As shown in (b), in an optical system employing a pure optical off-axis design, the central axis of the lens no longer coincides with the center of the LCD chip. This design alters the radius corresponding to the maximum field of view during optical design. In the projection device proposed in this embodiment, one edge (e.g., the long edge) of the display module (such as the LCD chip) is aligned with the central axis of the Fresnel lens and the lens. This spatial arrangement of optical components and the lens ensures that light emitted from the LCD chip, after being deflected by the Fresnel lens and refracted and modulated by the lens elements, ultimately allows the light to exit at or above the lens optical axis. After actual assembly, it will not be obstructed by the structural components at the bottom of the lens or the optical engine housing, allowing the imaging light to be accurately projected onto the screen, achieving a 100% off-axis projection imaging effect. For example, when the LCD chip is 3.0 inches in size, the offset between the center of the LCD chip and the center of the Fresnel lens and the lens reaches 18.68 mm (equivalent to half the height of the LCD), resulting in a field of view radius Y1 = 51.0 mm, which is much larger than the field of view radius of a lens without offset.

[0110] Therefore, with a 3.0-inch LCD chip, the maximum field of view (Y0) of a lens without off-axis projection is 38.1mm. However, this projection lens, employing a pure optical off-axis design with a 100% off-axis offset, achieves a maximum field of view (Y1) of 51.0mm, representing a 31% increase in field of view compared to the non-off-axis lens design. This optical design enables excellent imaging performance and reduces the loss of optical brightness and resolution after keystone correction when implementing off-axis projection, thus enhancing viewing comfort.

[0111] This application proposes a projection lens with excellent imaging performance indicators by adopting a lens layout of no less than 7G under the imaging performance requirements of LCD projection. This is achieved through the coordination of various lens materials, surface shapes, and air gaps, while meeting the design requirements of a 100% off-axis, large field of view. (Refer to...) Figure 6 , Figure 6A schematic diagram of the main ray propagation in Zemax imaging is shown, such as... Figure 6 As shown, the light emitted from each position in the display module (including the light emitted from the farthest point) is deflected by the Fresnel lens and refracted and modulated by the lens elements, so that the light can be emitted in the area at or above the optical axis of the lens. After actual assembly, it will not be blocked by the structural components at the bottom of the lens and the optical engine housing.

[0112] Figure 6 The images indicate the positions of the main ray on the LCD chip at 0% and 100% off-axis. Different main ray positions represent different field-of-view radii. Given a fixed imaging performance specification, a larger field-of-view radius increases design complexity and requires more optical lenses. For example, consider two lenses in currently mass-produced projectors without off-axis functionality: a 4.45-inch FHD chip with a pixel size of 51.31µm corresponds to a field-of-view radius of 56.51mm, requiring a minimum of 4 lenses; a 5.00-inch UHD chip with a pixel size of 28.83µm corresponds to a field-of-view radius of 63.50mm, requiring a minimum of 7 lenses. To achieve the same design performance, using a chip with a larger field of view and smaller pixel size requires more lens elements, increasing design complexity.

[0113] It's important to understand that a good lens design aims to achieve the desired imaging performance using the fewest possible lens elements. While a lens combination with fewer than seven elements can achieve 100% off-axis performance, the optimal imaging performance will be significantly lower than that presented in this embodiment. Similarly, a lens combination with more than seven elements can also achieve 100% off-axis performance, and the imaging performance may be similar to this embodiment, but compared to the lens proposed in this application, the design will be more complex and the actual engineering production cost will be higher.

[0114] This application's embodiments relate to the projection lens proposed in the above embodiments, and Figure 4 The optical performance of the projection device with 100% optical off-axis shown was tested. The test results are as follows.

[0115] This embodiment proposes an MTF evaluation for the aforementioned lens. The Modulation Transfer Function (MTF) is currently the most accurate and scientific evaluation standard for lenses. The vertical axis represents modulation contrast; the closer it is to 1, the better the lens's imaging performance. The horizontal axis represents resolution, measured in line pairs per millimeter. In the optical MTF graph, the horizontal axis values ​​increase sequentially from left to right; the further to the right, the finer the detail. For projection lenses, a minimum MTF value of 0.3 is generally required for each field of view at the designed resolution. For a 3.0-inch Full HD LCD chip, X = 14.5 / mm is sufficient to resolve the details of each pixel. (Refer to...) Figure 7 , Figure 7 A schematic diagram of the MTF of a projection lens is shown, such as Figure 7 As shown, for a 3.0-inch Full HD LCD chip, its spatial cutoff frequency is approximately 14.5 line pairs / mm (abbreviated as 14.5 lap / mm), and its optical transfer function across the entire field of view has a value greater than 0.35 at the cutoff frequency, exhibiting excellent imaging quality.

[0116] Reference Figure 8 , Figure 8 A field curvature diagram and relative distortion diagram of a projection lens are shown, such as... Figure 8 As shown, Figure 8 (a) in the figure is the field curvature diagram of the projection lens. The vertical axis represents the field of view of the optical system, and the horizontal axis represents the image surface deviation of the optical system, that is, the deviation distance between the actual image surface and the ideal image surface (such as the paraxial image surface or the flat image surface), which is used to intuitively reflect the degree of curvature of the image surface. Figure 8 (b) in the diagram is the Relative Distortion Diagram (RDD), an optical performance chart used to quantify and visualize lens distortion (image deformation). It visually displays the degree of distortion at different field of view (or image height). The RDD uses a curve to show the percentage deviation between the actual image height and the ideal image height as a function of the field of view (or image height). The horizontal axis represents the field of view or normalized image height (0% is the optical axis center, 100% is the image field edge), and the vertical axis represents the percentage of distortion (positive values ​​indicate pincushion distortion, negative values ​​indicate barrel distortion). Figure 8 It can be seen that the absolute values ​​of field curvature in both the meridional and sagittal directions are relatively small; the maximum optical distortion is 0.0280%, which is a very good level for a large field-of-view lens design with minimal distortion of the projected image.

[0117] Reference Figure 9 , Figure 9 This diagram illustrates the TV distortion of a projection lens. TV distortion (Television Distortion) is an indicator used in optical systems to quantify the geometric deformation of an image. It measures the degree of curvature of straight lines at the edges of the image due to distortion during lens imaging, and is usually expressed as a percentage (%). Figure 9 As shown, this embodiment employs a grid testing method, projecting a standard grid pattern (such as a checkerboard or square grid), capturing the projected image, measuring the maximum curvature (ΔL) of the edge lines, and calculating the TV distortion value. In a 16:9 grid, the absolute value of TV distortion is controlled to 0.02%, far lower than the conventional 0.3%. This demonstrates that the projection lens proposed in this embodiment performs excellent image distortion control when achieving large field-of-view imaging display.

[0118] Reference Figure 10 , Figure 10 This diagram illustrates the lateral chromatic aberration (LCA) of a projection lens. The LCA is an optical performance chart used to quantify and visualize the lateral chromatic aberration (also known as "lateral color difference" or "magnification color difference") of a lens. It visually shows the positional shift of light of different wavelengths (colors) on the imaging plane, directly affecting the color edge sharpness of the projected image. The vertical axis represents the image height field of view value, and the horizontal axis represents the lateral shift of different wavelengths of light (or the deviation relative to the dominant wavelength (such as green light), in micrometers). The diagram uses the wavelength of green light as a reference wavelength and plots the chromatic aberration values ​​for each field of view between blue light, red light, and green light (dominant wavelength), as shown below. Figure 10 As shown, the maximum deviation of the chromatic difference along the reference wavelength of the projection lens proposed in this embodiment (compared to the reference wavelength) is less than 11µm.

[0119] Reference Figure 11 , Figure 11 This diagram illustrates a relative illumination diagram for a projection lens. A relative illumination diagram is an optical performance chart used to quantify the uniformity of brightness between the edge and center of the lens's imaging surface, visually reflecting the light intensity attenuation at different field of view angles. The horizontal axis represents the normalized image height (0% at the optical axis center, 100% at the image field edge) or field of view angle. The vertical axis represents the percentage of relative illumination (usually 100% at the center; lower values ​​at the edges indicate more severe attenuation). Figure 11 As shown, at the position of maximum field of view Y = 51.0mm, the relative illuminance value is ≥70%, indicating that the difference between the edge brightness and the center brightness of the projected image is small and the brightness uniformity is good. Therefore, the projection lens proposed in this application embodiment can better avoid the difference in brightness caused by the low corner brightness of the projected image.

[0120] Therefore, this application discloses a 3.0-inch LCD projection lens with 100% off-axis projection. The lens uses a combination of 7 lenses in 7 groups. The optical system of the projection lens, from the magnification side to the reduction side, sequentially includes a convex-concave negative lens G01, a convex-concave positive lens G02, a convex-concave negative lens G03, a biconvex positive lens G04, a concave-convex positive lens G05, a biconcave negative lens G06, and a concave-convex positive lens G07 in the opposite direction of light. In a practical projection optical system, the lens described in this embodiment can provide excellent projection image quality (based on the above design performance) and a comfortable viewing experience while achieving 100% off-axis projection. Furthermore, the projection lens proposed in this application embodiment has a projection ratio of 1.25:1, a resolution of 1920x1080, an LCD offset of 100% from the lens optical axis, a relative aperture of F=3.0, a back working distance of 65.98mm, a total lens length of 77.86mm, a total optical system length of 155.34mm, a 3.0-inch LCD panel chip, and a Fresnel lens with an equivalent focal length of 90mm. The projection lens adopts a pure optical off-axis design, which has extremely low optical distortion and TV distortion, enhances viewing comfort, reduces the loss of image resolution and brightness when physically off-axis irradiates the screen, and improves the performance of the projected image.

[0121] A second aspect of this application also provides another projection lens, the lens comprising at least:

[0122] A first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, and a seventh lens are arranged sequentially with their optical axes overlapping, from the image side to the object side along the opposite direction of light transmission; wherein, the image side is the side of the projection lens closest to the projection imaging surface, and the object side is the side of the projection lens closest to the original image being projected.

[0123] The optical power matching relationship between the first lens, the second lens, and the third lens is as follows: the first lens has negative optical power, the second lens has positive optical power, and the third lens has negative optical power.

[0124] In one possible implementation, the optical power matching relationship between the fourth lens, the fifth lens, the sixth lens, and the seventh lens is as follows: the fourth lens has positive optical power, the fifth lens has positive optical power, the sixth lens has negative optical power, and the seventh lens has positive optical power.

[0125] The structure of the projection lens proposed in the embodiments of this application is as follows: Figure 3As shown. Optical power is an optical concept used to characterize the refractive power of an optical lens or lens group to a light beam. The larger the optical power value, the stronger the refraction of light. When the optical power is positive, it converges parallel light; when the optical power is negative, it reflects parallel light. This application proposes a projection lens suitable for 100% off-axis LCD scenarios. Through optical design (the optical power matching relationship between various lenses), it can achieve excellent imaging performance. In particular, while achieving 100% optical off-axis projection, it can reduce the loss of optical brightness and resolution after keystone correction, and has excellent imaging optical performance, enhancing viewing comfort.

[0126] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0127] A third aspect of this application also provides a projection device, the device comprising:

[0128] The projection lens described in the first or second aspect of the embodiments of this application;

[0129] The display module emits light into the projection lens and exits from the projection lens.

[0130] In this embodiment, the display module may include an LCD chip. The projection device proposed in this application embodiment can be used in application scenarios where the LCD optical off-axis is 100%. This embodiment proposes to achieve 100% optical off-axis by changing the relative position between the projection lens and the display module.

[0131] In one possible implementation, the device further includes:

[0132] A Fresnel lens is disposed with its optical axis aligned with that of the projection lens, and the Fresnel lens is located between the display module and the projection lens;

[0133] The plane containing the Fresnel lens is parallel to the plane containing the display module. One side of the display module is aligned with the optical axis of the Fresnel lens, and the light emission direction of the display module is parallel to the extension direction of the optical axis of the projection lens.

[0134] In one possible implementation, the air gap between the projection lens and the Fresnel lens is greater than or equal to 65.72 mm and less than or equal to 66.88 mm; the air gap between the Fresnel lens and the display module is greater than or equal to 10.74 mm and less than or equal to 12.00 mm.

[0135] In this embodiment, the structure of the projection device is as follows: Figure 4 As shown, one side of the display module (LCD chip) lies on the optical axis of the Fresnel lens. Further, the display module can be rectangular, with one long side of the display module lying along the extension direction of the lens's optical axis. Figure 4 As shown, the light emitted from a long side of the display module away from the optical axis can be emitted through the projection lens, thereby achieving 100% optical off-axis.

[0136] In one possible implementation, the light emission direction of the display module is perpendicular to the optical axis extension direction of the projection lens, and the device further includes:

[0137] Fresnel lenses and mirrors;

[0138] The plane containing the Fresnel lens is parallel to the plane containing the display module. The Fresnel lens is located between the display module and the reflector. The reflector is used to reflect the light from the display module that has passed through the Fresnel lens to the projection lens.

[0139] One side of the display module is aligned with the optical axis of the Fresnel lens, and the light emission direction of the display module is parallel to the extension direction of the optical axis of the Fresnel lens.

[0140] Reference Figure 12 , Figure 12 A schematic diagram of another projection device is shown, such as Figure 12 As shown, in actual optical engines, projection lenses can work with reflectors to bend the light path, achieving an "L"-shaped architecture to meet the system's spatial design requirements. For example... Figure 12 As shown, the projection device may also include a projection lighting system for providing light to the display module. The display module (such as...) Figure 12 Light emitted from one edge of the LCD chip (as shown) passes through the center of the Fresnel lens (so one edge of the display module is on the optical axis of the Fresnel lens), then strikes the reflective surface of the mirror along the solid arrow, and is reflected by the mirror before entering the lens along the optical axis. Light from the other edge of the LCD chip, after being refracted by the Fresnel lens, strikes the reflective surface of the mirror along the solid arrow, and is reflected by the mirror before entering the lens from the edge. The light rays at these two boundary positions define the propagation range of the imaging light, allowing the imaging light to be accurately projected onto the screen along a set path, creating a 100% off-axis projection imaging effect. Furthermore, if the actual light rays are traced in reverse at the mirror interface (equivalent to light rays without mirror deflection), the same as... Figure 3 It has the same cylindrical structure. Since only half of the effective area of ​​the Fresnel lens is used, in the actual reflected light path, the Fresnel lens is used after being cut in half along the center position.

[0141] In one possible implementation, the Fresnel lens has a focal length of 90 mm, a positive curvature along the light emission direction and a negative curvature in the opposite direction, a radius of curvature greater than or equal to -45.2 mm and less than or equal to -44.1 mm, a thickness greater than or equal to 1.60 mm and less than or equal to 2.00 mm, a refractive index greater than or equal to 1.49 and less than or equal to 1.50, and a dispersion coefficient greater than or equal to 57.3 and less than or equal to 57.4.

[0142] In one possible implementation, the display module is 3.0 inches in size. The display module can be a 3.0-inch LCD chip.

[0143] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0144] Finally, it should be noted that in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0145] The foregoing has provided a detailed description of a projection lens and projection device provided in this application. Specific examples have been used to illustrate the principles and implementation methods of this application. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

[0146] Other embodiments of this application will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of this application are indicated by the following claims.

[0147] It should be understood that this application 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 this application is limited only by the appended claims.

[0148] The terms "an embodiment," "embodiment," or "one or more embodiments" as used herein mean that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment of this application. Furthermore, please note that the examples of the phrase "in one embodiment" do not necessarily all refer to the same embodiment.

[0149] Numerous specific details are set forth in the specification provided herein. However, it will be understood that embodiments of this application may be practiced without these specific details. In some instances, well-known methods, structures, and techniques have not been shown in detail so as not to obscure the understanding of this specification.

[0150] In the claims, any reference signs placed between parentheses should not be construed as limiting the claims. The word "comprising" does not exclude the presence of elements or steps not listed in the claims. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. This application can be implemented by means of hardware comprising several different elements and by means of a suitably programmed computer. In a unit claim enumerating several means, several of these means may be embodied by the same item of hardware. The use of the words first, second, and third, etc., does not indicate any order. These words can be interpreted as names.

[0151] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A projection lens, characterized in that, The lens includes at least: A first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, and a seventh lens are arranged sequentially with their optical axes overlapping, from the image side to the object side along the opposite direction of light transmission; wherein, the image side is the side of the projection lens closest to the projection imaging surface, and the object side is the side of the projection lens closest to the original image being projected. Among them, the first lens, the second lens and the third lens are all convex and concave lenses, with the image side being convex and the object side being concave; The fourth lens is a biconvex lens; The fifth lens is a concave-convex lens, with the image side being concave and the object side being convex. The sixth lens is a biconcave lens; The seventh lens is a concave-convex lens, with the image side being concave and the object side being convex.

2. The projection lens according to claim 1, characterized in that The optical power matching relationship between the first lens, the second lens, and the third lens is as follows: the first lens has negative optical power, the second lens has positive optical power, and the third lens has negative optical power.

3. The projection lens of claim 1, wherein The optical power matching relationship between the fourth lens, the fifth lens, the sixth lens, and the seventh lens is as follows: the fourth lens has positive optical power, the fifth lens has positive optical power, the sixth lens has negative optical power, and the seventh lens has positive optical power.

4. The projection lens of claim 1, wherein The radius of curvature of the image side of the first lens is greater than the radius of curvature of the object side of the first lens; The radius of curvature of the image side of the second lens is smaller than the radius of curvature of the object side of the second lens; The radius of curvature of the image side of the third lens is greater than the radius of curvature of the object side of the third lens. The radius of curvature of the image side of the fourth lens is smaller than the radius of curvature of the object side of the fourth lens. The radius of curvature of the image side of the fifth lens is greater than the radius of curvature of the object side of the fifth lens; The radius of curvature of the image side of the sixth lens is smaller than the radius of curvature of the object side of the sixth lens. The radius of curvature of the image side of the seventh lens is greater than the radius of curvature of the object side of the seventh lens.

5. The projection lens according to claim 4, characterized in that With the curvature along the direction of light emission being positive and the curvature in the opposite direction being negative, the radius of curvature of the image side of the first lens is greater than or equal to 41.5 mm and less than or equal to 42.6 mm; the radius of curvature of the object side is greater than or equal to 27.4 mm and less than or equal to 28.5 mm. The radius of curvature of the image side of the second lens is greater than or equal to 41.8 mm and less than or equal to 42.9 mm; the radius of curvature of the object side is greater than or equal to 95.1 mm and less than or equal to 96.2 mm. The radius of curvature of the image side of the third lens is greater than or equal to 109.9 mm and less than or equal to 111.0 mm; the radius of curvature of the object side is greater than or equal to 32.9 mm and less than or equal to 34.0 mm. The radius of curvature of the image side of the fourth lens is greater than or equal to 65.4 mm and less than or equal to 66.5 mm; the radius of curvature of the object side is greater than or equal to -146.7 mm and less than or equal to -144.6 mm. The radius of curvature of the image side of the fifth lens is greater than or equal to -2856.7 mm and less than or equal to -2854.6 mm; the radius of curvature of the object side is greater than or equal to -43.6 mm and less than or equal to -41.5 mm. The radius of curvature of the image side of the sixth lens is greater than or equal to -54.9 mm and less than or equal to -53.8 mm; the radius of curvature of the object side is greater than or equal to 74.3 mm and less than or equal to 75.4 mm. The radius of curvature of the image side of the seventh lens is greater than or equal to -204.6 mm and less than or equal to -203.5 mm; the radius of curvature of the object side is greater than or equal to -67.2 mm and less than or equal to -66.1 mm.

6. The projection lens according to claim 1, characterized in that, The center thickness of the first lens is less than the center thickness of the third lens, and the center thickness of the third lens is less than the center thickness of the second lens; wherein, the center thickness is the thickness of the lens at its center along the optical axis. The center thickness of the sixth lens is less than the center thickness of the seventh lens, the center thickness of the seventh lens is less than the center thickness of the fifth lens, and the center thickness of the fifth lens is less than the center thickness of the fourth lens; The center thickness of the fourth lens is greater than the center thickness of the third lens, but less than the center thickness of the second lens.

7. The projection lens of claim 1, wherein The refractive index of the first lens is less than that of the third lens, and the refractive index of the third lens is less than that of the second lens; The refractive index of the fifth lens is less than that of the sixth lens, and the refractive index of the sixth lens is less than that of the fourth lens or the seventh lens; The refractive index of the fifth lens is less than that of the third lens.

8. The projection lens of claim 1, wherein, The dispersion coefficient of the third lens is smaller than that of the second lens, and the dispersion coefficient of the second lens is smaller than that of the first lens. The dispersion coefficient of the sixth lens is less than that of the fourth lens or the seventh lens, and the dispersion coefficient of the fourth lens or the seventh lens is less than that of the fifth lens. The dispersion coefficient of the sixth lens is smaller than that of the third lens.

9. The projection lens of claim 1, wherein, The second lens, the fourth lens, and the seventh lens have the same refractive index and the same dispersion coefficient.

10. The projection lens of claim 1, wherein, The focal length ratio of the first lens to the second lens is greater than or equal to -2.2 and less than or equal to -2.1; The focal length ratio of the third lens to the second lens is greater than or equal to -1.1 and less than or equal to -1.

0. The focal length ratio between the fourth lens and the sixth lens is greater than or equal to -1.4 and less than or equal to -1.

3. The focal length ratio of the fifth lens to the sixth lens is greater than or equal to -2.2 and less than or equal to -2.1; The focal length ratio of the seventh lens to the sixth lens is greater than or equal to -2.2 and less than or equal to -2.

1.

11. The projection lens of claim 1, wherein, The lens further includes an aperture stop, which is located between the third lens and the fourth lens; The air gap between the first lens and the second lens is greater than the air gap between the second lens and the third lens; The air gap between the second lens and the third lens is greater than the air gap between the third lens and the aperture stop; The air gap between the third lens and the aperture stop is greater than the air gap between the sixth lens and the seventh lens; The air gap between the sixth lens and the seventh lens is greater than the air gap between the fourth lens and the fifth lens; The air gap between the fourth lens and the fifth lens is greater than the air gap between the aperture stop and the fourth lens; and the air gap between the fourth lens and the fifth lens is greater than the air gap between the fifth lens and the sixth lens.

12. The projection lens according to claim 1, characterized in that, The aperture of the first lens is larger than the aperture of the second lens; The aperture of the second lens is larger than that of the seventh lens; The aperture of the seventh lens is larger than that of the sixth lens; The aperture of the sixth lens is larger than that of the third lens; The aperture of the third lens is larger than that of the fifth lens; The aperture of the fifth lens is larger than that of the fourth lens.

13. A projection lens characterized by, The lens includes at least: A first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, and a seventh lens are arranged sequentially with their optical axes overlapping, from the image side to the object side along the opposite direction of light transmission; wherein, the image side is the side of the projection lens closest to the projection imaging surface, and the object side is the side of the projection lens closest to the original image being projected. The optical power matching relationship between the first lens, the second lens, and the third lens is as follows: the first lens has negative optical power, the second lens has positive optical power, and the third lens has negative optical power.

14. The projection lens of claim 13, wherein, The optical power matching relationship between the fourth lens, the fifth lens, the sixth lens, and the seventh lens is as follows: the fourth lens has positive optical power, the fifth lens has positive optical power, the sixth lens has negative optical power, and the seventh lens has positive optical power.

15. A projection apparatus, characterized by comprising: The device includes: The projection lens according to any one of claims 1-14; The display module emits light into the projection lens and exits from the projection lens.

16. The projection apparatus according to claim 15, wherein, The device further includes: A Fresnel lens is disposed with its optical axis aligned with that of the projection lens, and the Fresnel lens is located between the display module and the projection lens; The plane containing the Fresnel lens is parallel to the plane containing the display module. One side of the display module is aligned with the optical axis of the Fresnel lens, and the light emission direction of the display module is parallel to the extension direction of the optical axis of the projection lens.

17. The projection apparatus according to claim 16, wherein The air gap between the projection lens and the Fresnel lens is greater than or equal to 65.72 mm and less than or equal to 66.88 mm; the air gap between the Fresnel lens and the display module is greater than or equal to 10.74 mm and less than or equal to 12.00 mm.

18. The projection apparatus of claim 15, wherein The light emission direction of the display module is perpendicular to the optical axis extension direction of the projection lens, and the device further includes: Fresnel lenses and mirrors; The plane containing the Fresnel lens is parallel to the plane containing the display module. The Fresnel lens is located between the display module and the reflector. The reflector is used to reflect the light from the display module that has passed through the Fresnel lens to the projection lens. One side of the display module is aligned with the optical axis of the Fresnel lens, and the light emission direction of the display module is parallel to the extension direction of the optical axis of the Fresnel lens.

Images