Projection lens, projection system and projection device

Abstract

This application discloses a projection lens, a projection system, and a projection device. The projection lens includes a first lens group, an aperture, and a second lens group. The first lens group includes a first lens, a second lens, a third lens, a fourth lens, and a fifth lens. The first lens has negative refractive power, the second lens has positive refractive power, the third lens has negative refractive power, the fourth lens has negative refractive power, and the fifth lens has positive refractive power. The second lens group includes a sixth lens, a seventh lens, an eighth lens, a ninth lens, and a tenth lens. The sixth lens has positive refractive power, the seventh lens has negative refractive power, the eighth lens has positive refractive power, the ninth lens has positive refractive power, and the tenth lens has positive refractive power. The projection lens satisfies at least one of the following conditions: 1.6 ≤ BFL / EFL ≤ 2.5; BFL / TTL ≥ 0.3. The projection lens provided by this application can achieve a small size while improving the performance of the projection lens.

Description

Technical Field

[0001] This application relates to the field of projection imaging, and more particularly to a projection lens, projection system, and projection device. Background Technology

[0002] As projectors are increasingly used across various fields, the projection lens determines the image quality, and its design is constantly being improved and optimized. Currently, there are greater demands for smaller projector sizes, requiring more compact and smaller projection lens structures. This presents certain challenges to the performance of projection lenses, and the performance of existing lenses needs improvement. Summary of the Invention

[0003] This application provides a projection lens, a projection system, and a projection device, which can improve the performance of the projection lens.

[0004] An embodiment of the first aspect of this application provides a projection lens, which includes, along the optical axis from the magnification side to the reduction side, a first lens group having negative optical power, an aperture stop, and a second lens group having positive optical power; the first lens group includes a first lens, a second lens, a third lens, a fourth lens, and a fifth lens arranged sequentially along the optical axis from the magnification side to the reduction side, wherein the first lens has negative refractive power, the second lens has positive refractive power, the third lens has negative refractive power, the fourth lens has negative refractive power, and the fifth lens has positive refractive power; the second lens group... The projection lens comprises a sixth lens, a seventh lens, an eighth lens, a ninth lens, and a tenth lens arranged sequentially along the optical axis from the magnification side to the reduction side. The sixth lens has positive refractive power, the seventh lens has negative refractive power, the eighth lens has positive refractive power, the ninth lens has positive refractive power, and the tenth lens has positive refractive power. The focal length of the projection lens is EFL, the back focal length of the projection lens is BFL, and the total optical length of the projection lens is TTL. The projection lens satisfies at least one of the following conditions: 1.6≤BFL / EFL≤2.5; BFL / TTL≥0.3.

[0005] According to an embodiment of the first aspect of this application, the first lens group further includes an eleventh lens, which is disposed between the second lens and the third lens, and the eleventh lens has negative refractive power; and / or, the second lens group further includes a twelfth lens, which is disposed between the aperture stop and the eighth lens, and the twelfth lens has negative refractive power.

[0006] According to any of the foregoing embodiments of the first aspect of this application, the fourth lens and the fifth lens constitute a cemented doublet lens group with positive refractive power; and / or, the sixth lens, the seventh lens and the eighth lens constitute a cemented triplet lens group with positive refractive power.

[0007] According to any of the foregoing embodiments of the first aspect of this application, the refractive index of the fourth lens is less than that of the fifth lens; and / or, the refractive indices of the sixth and eighth lenses are both less than that of the seventh lens.

[0008] According to any of the foregoing embodiments of the first aspect of this application, the fourth lens is a biconcave negative lens, the fifth lens is a biconvex positive lens; and / or, the sixth lens is a biconvex positive lens, the seventh lens is a biconcave negative lens, and the eighth lens is a biconvex positive lens.

[0009] According to any of the foregoing embodiments of the first aspect of this application, the image plane height of the projection lens is H, the aperture number of the projection lens is Fno, and the outer diameter of the largest lens in the projection lens is L. MAX The projection lens satisfies at least one of the following relationships: 8 ≤ TTL / H ≤ 22; 10mm ≤ L MAX / Fno≤25mm.

[0010] According to any of the foregoing embodiments of the first aspect of this application, the focal length of the first lens group is EFL. ZOOM1 The focal length of the second lens group is EFL. ZOOM2 And it satisfies the following relationship: -65.0 < EFL ZOOM1 / EFL < -30.0; 0.5 < EFL ZOOM2 / EFL < 2.5.

[0011] According to any of the foregoing embodiments of the first aspect of this application, the aperture number of the projection lens is Fno, and the projection lens satisfies at least one of the following relationships: 8mm≤EFL≤25mm; TTL≤180mm; BFL≥20mm; Fno≤2.8; and the diameter of each lens is not greater than 50mm.

[0012] According to any of the foregoing embodiments of the first aspect of this application, the lenses of the projection lenses are all all-glass spherical lenses.

[0013] According to any of the foregoing embodiments of the first aspect of this application, the second lens group includes at least two lenses with a refractive index greater than 1.8; and / or, the second lens group includes X lenses with a negative ratio of refractive index temperature coefficient to focal length, and satisfies the following relationship: 1≤X≤4.

[0014] The second aspect of this application also provides a projection system, which includes a projection lens according to any of the embodiments of the first aspect described above.

[0015] A third aspect of this application also provides a projection device, which includes a projection lens of any embodiment of the first aspect or a projection system of the second aspect.

[0016] In a projection lens provided in this application, the projection lens includes a first lens group, an aperture stop, and a second lens group. By rationally setting the positive and negative refractive powers of each lens in the first and second lens groups, the projection lens structure is made precise, achieving the goals of low cost, compactness, and small size. The first lens group G1 is responsible for light collection and correction of distortion and other off-axis aberrations. The second lens group G2 is responsible for controlling the image-side telecentric angle and correcting chromatic aberration and other off-axis aberrations. The first lens group G1 undertakes the distortion correction capability, which is beneficial to improving the field of view of the system. It can effectively correct off-axis aberrations such as distortion, coma, field curvature, and astigmatism, ensuring a relatively smooth incident angle between the light and the lens surface, providing a large field of view without generating large higher-order aberrations. By rationally planning the refractive powers of each lens, it is beneficial to ensure a smooth light transition and the stability of the image. By limiting the ratio of the back focal length (BFL) to the focal length (EFL) of the projection lens to within the range of [1.6, 2.5], a longer back focal length can be achieved, providing favorable conditions for brightness, structure, and heat dissipation, thereby improving the performance of the projection lens. Furthermore, by limiting the ratio of the back focal length (BFL) to the total optical length (TTL) to be greater than or equal to 0.3, the projection lens can achieve a longer back focal length while maintaining a short lens length. This allows for miniaturization of projection devices using this lens, further improving its performance. In summary, this application improves the performance of projection lenses. Attached Figure Description

[0017] 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 the same or similar reference numerals denote the same or similar features.

[0018] Figure 1 This is a schematic diagram of the structure of a projection lens provided in the first aspect embodiment of this application;

[0019] Figure 2 This is a schematic diagram of another projection lens provided in the first aspect embodiment of this application;

[0020] Figure 3 This is a schematic diagram of the structure of another projection lens provided in the first aspect of this application.

[0021] Explanation of reference numerals in the attached figures:

[0022] G1, First lens group; S, Aperture stop; G2, Second lens group; P, Prism; CG, Protective glass; DMD, Digital microlens device; SCR, Projection screen;

[0023] L1, First lens; L2, Second lens; L3, Third lens; L4, Fourth lens; L5, Fifth lens; L6, Sixth lens; L7, Seventh lens; L8, Eighth lens; L9, Ninth lens; L10, Tenth lens; L11, Eleventh lens; L12, Twelfth lens. Detailed Implementation

[0024] The features and exemplary embodiments of various aspects of this application will now be described in detail. Numerous specific details are set forth in the following detailed description to provide a comprehensive understanding of this application. However, it will be apparent to those skilled in the art that this application can be implemented without requiring some of these specific details. The following description of embodiments is merely intended to provide a better understanding of this application by illustrating examples. In the accompanying drawings and the following description, at least some well-known structures and techniques are not shown to avoid unnecessarily obscuring the application; and, for clarity, the dimensions of some structures may be exaggerated. Furthermore, the features, structures, or characteristics described below can be combined in any suitable manner in one or more embodiments.

[0025] In the description of this application, it should be noted that, unless otherwise stated, "a plurality of" means two or more; the terms "upper," "lower," "left," "right," "inner," "outer," etc., indicating orientation or positional relationships are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this application. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Moreover, 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..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0026] The directional terms appearing in the following description refer to the directions shown in the figures and are not intended to limit the specific structure of the embodiments of this application. It should also be noted in the description of this application that, unless otherwise explicitly specified and limited, the terms "installation" and "connection" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0027] As projectors are increasingly used across various fields, the projection lens determines the image quality, and its design is constantly being improved and optimized. Currently, there are greater demands for smaller projector sizes, requiring more compact and smaller projection lenses. This presents certain challenges to lens performance, necessitating both small size and consistent performance, as well as cost reduction.

[0028] This application is proposed to solve the aforementioned technical problems. To better understand this application, the following is combined with... Figures 1 to 3 The projection lens, projection system, and projection device of the present application are described in detail.

[0029] The projection lens in this application embodiment can be a projection lens of a projector. Optionally, the projection lens can be a projection lens of a laser projector. Laser projectors have the characteristics of high image contrast, clear imaging, vivid colors, and higher brightness. Optionally, the projection lens in this application embodiment can also be applied to LED (Light Emitting Diode) projectors, LCD (Liquid Crystal Display) projectors, etc. The projection lens in this application embodiment is not limited to a projection lens of a projector; if other devices use the projection lens provided in this application, they should also fall within the protection scope of this application.

[0030] The projection lens of this application embodiment can be applied to a fixed-focus projection lens of a projector. The fixed-focus projection lens also includes a prism P, a protective glass CG, and a digital micromirror device (DMD) chip. The first lens group G1, the aperture S, the second lens group G2, the prism P, the protective glass CG, and the digital micromirror device DMD are arranged along the optical axis from the magnification side to the reduction side. During projection, light enters the projection lens from the image plane side of the DMD, passes through the protective glass CG and the prism P, and finally exits the projection lens to the projection screen SCR (Screen), thus obtaining the projection imaging effect. For example, the projection lens can be applied to an in-vehicle projection system or an in-vehicle projection device.

[0031] Please refer to the following: Figure 1 , Figure 1 This is a schematic diagram of the structure of a projection lens provided in the first aspect of this application.

[0032] like Figure 1As shown, an embodiment of the first aspect of this application provides a projection lens, which includes, along the optical axis from the magnification side to the reduction side, a first lens group G1 having negative optical power, an aperture stop S, and a second lens group G2 having positive optical power; the first lens group G1 includes a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, and a fifth lens L5 arranged sequentially along the optical axis from the magnification side to the reduction side, wherein the first lens L1 has negative refractive power, the second lens L2 has positive refractive power, the third lens L3 has negative refractive power, the fourth lens L4 has negative refractive power, and the fifth lens L5 has positive refractive power; the second... Lens group G2 includes a sixth lens L6, a seventh lens L7, an eighth lens L8, a ninth lens L9, and a tenth lens L10 arranged sequentially along the optical axis from the magnification side to the reduction side. The sixth lens L6 has positive refractive power, the seventh lens L7 has negative refractive power, the eighth lens L8 has positive refractive power, the ninth lens L9 has positive refractive power, and the tenth lens L10 has positive refractive power. The focal length of the projection lens is EFL, the back focal length of the projection lens is BFL, and the total optical length of the projection lens is TTL. The projection lens satisfies at least one of the following conditions: 1.6≤BFL / EFL≤2.5; BFL / TTL≥0.3.

[0033] In this embodiment, the magnifying side refers to the side of the projection lens that is closer to the SCR projection screen when the projection lens is applied to the projection system or projection device, and the shrinking side refers to the side of the projection lens that is closer to the DMD.

[0034] In this embodiment, the back focal length of the projection lens can also be called the back focal length; the focal length of the projection lens can also be called the effective focal length. Optionally, the total optical length of the projection lens is TTL, which is the axial distance along the optical axis between the magnifying side of the first lens L1 and the DMD. The back focal length of the projection lens refers to the distance along the optical axis between the reducing side of the lens closest to the DMD and the DMD chip. Optionally, the back focal length of the projection lens is equal to the distance along the optical axis between the reducing side of the tenth lens L10 and the DMD.

[0035] Optionally, the projection lens satisfies the following relationship: 1.6≤BFL / EFL≤2.5; BFL / TTL≥0.3.

[0036] For example, the BFL / EFL ratio can be 2.5, 2.45, 2.4, 2.3, 2.2, 2.1, 2, 1.9, 1.8, 1.7, or 1.6, etc. The BFL / EFL ratio can also be any combination of the above values. The BFL / TTL ratio can be 0.3, 0.32, 0.35, 0.4, 0.45, 0.48, or 0.5, etc. The BFL / TTL ratio can also be any combination of the above values.

[0037] Optionally, the aperture stop S is a variable aperture stop, which can continuously adjust the size of the opening. By adjusting the size of the aperture stop S, the brightness of the projection lens can be changed to achieve different applications. For example, when high brightness is required, the aperture stop S can be adjusted to the maximum, and when in a darker environment, the aperture stop S can be reduced.

[0038] In this embodiment, the first lens group G1, the aperture S, and the second lens group G2 are arranged sequentially from the magnifying side to the reducing side along the optical axis. During projection, light rays from the light source pass sequentially through the second lens group G2, the aperture S, and the first lens group G1 from the image plane side, and are finally projected onto the projection screen SCR. The projection lens includes at least ten lenses. By reasonably setting the positive and negative refractive powers of each lens in the first lens group G1 and the second lens group G2, the structure of the projection lens is made precise, thereby achieving the goals of low cost, compactness, and small size.

[0039] In the projection lens of this application embodiment, the projection lens includes a first lens group G1, an aperture S and a second lens group G2. The aperture S can be used to gather the light from the front and back, which is beneficial to shorten the total length of the projection lens.

[0040] The first lens group G1 collects light and corrects distortion and other off-axis aberrations. The second lens group G2 controls the image-side telecentric angle and corrects chromatic aberration and other off-axis aberrations. The first lens group G1 provides distortion correction, which helps to increase the system's field of view. It effectively corrects off-axis aberrations such as distortion, coma, field curvature, and astigmatism, ensuring a relatively smooth angle of incidence between the light and the lens surface, providing a large field of view without producing large higher-order aberrations. By rationally planning the refractive power of each lens, a smooth light transition is ensured, contributing to the stability of the image.

[0041] By limiting the ratio of the back focal length (BFL) to the focal length (EFL) of the projection lens to within the range of [1.6, 2.5], a longer back focal length can be achieved, providing favorable conditions for brightness, structure, and heat dissipation, thereby improving the performance of the projection lens. Furthermore, by limiting the ratio of the back focal length (BFL) to the total optical length (TTL) to be greater than or equal to 0.3, the projection lens can achieve a longer back focal length while maintaining a short lens length. This allows for miniaturization of the projection device using this lens, further improving its performance. In summary, the embodiments of this application can improve the performance of projection lenses.

[0042] In the projection lens of this application embodiment, the MTF (Modulation Transfer Function) performance can be improved by setting the parameters of each lens, so that the lens has good imaging quality and at the same time reduces system distortion.

[0043] When the radius of curvature of the magnifying side of a lens is positive, the magnifying side is convex; otherwise, it is concave. When the radius of curvature of the reducing side of a lens is negative, the reducing side is convex; otherwise, it is concave. When the radius of curvature of the magnifying side of a lens is ±∞, the magnifying side is flat. When the radius of curvature of the reducing side of a lens is ±∞, the reducing side is flat.

[0044] In some embodiments, the first lens group G1 further includes an eleventh lens L11, which is disposed between the second lens L2 and the third lens L3, and has negative refractive power. By reasonably setting the curvature and thickness of the eleventh lens L11, off-axis aberrations and system distortions can be effectively corrected, improving MTF performance. Optionally, the eleventh lens L11 can be a meniscus negative lens, with its magnifying side being convex and its reducing side being concave.

[0045] In some embodiments, the second lens group G2 further includes a twelfth lens L12, which is disposed between the aperture stop S and the eighth lens L8, and has negative refractive power. By reasonably setting the curvature and thickness of the twelfth lens L12, off-axis aberrations and system distortions can be effectively corrected, improving MTF performance. Optionally, the twelfth lens L12 can be a meniscus negative lens, with its magnifying side being convex and its reducing side being concave.

[0046] In some embodiments, the fourth lens L4 and the fifth lens L5 form a cemented doublet with positive refractive power.

[0047] In some embodiments, the sixth lens L6, the seventh lens L7, and the eighth lens L8 constitute a triplex lens group with positive refractive power.

[0048] A cemented doublet lens group is a lens group formed by cementing two lenses together, while a cemented triplet lens group is a lens group formed by cementing three lenses together, with the cemented surfaces of adjacent lenses touching each other.

[0049] In these embodiments, by cementing two lenses, the fourth lens L4 and the fifth lens L5, and cementing three lenses, the sixth lens L6, the seventh lens L7, and the eighth lens L8, together to form a cemented lens, it is beneficial to correct chromatic aberration and reduce the air gap between the lenses, thereby compressing the overall optical length of the system.

[0050] In addition, in the embodiments of this application, only one set of cemented doublet lens group and one set of cemented triplet lens group can be set, thereby reducing the cost of the projection lens.

[0051] In some embodiments, the refractive index of the fourth lens L4 is less than that of the fifth lens L5. The difference in their refractive indices can be greater than or equal to 0.2.

[0052] In some embodiments, the refractive indices of the sixth lens L6 and the eighth lens L8 are both less than the refractive index of the seventh lens L7. The difference in refractive index between the seventh lens L7 and the sixth lens L6 or the eighth lens L8 can be greater than or equal to 0.2.

[0053] In these embodiments, the combination of refractive power and refractive index of multiple lenses in the cemented lens group can effectively correct system chromatic aberration, and the cancellation of positive and negative spherical aberrations on the cemented surface can achieve the overall spherical aberration correction effect of the projection lens, thereby ensuring both image quality and simple structure of the projection lens.

[0054] Optionally, the fourth lens L4 and the fifth lens L5 are paired as a low-refractive-index and a high-refractive-index combination, and the sixth lens L6, the seventh lens L7, and the eighth lens L8 are paired as a low-refractive-index, a high-refractive-index, and a low-refractive-index combination. A lens with a high refractive index is a lens with a refractive index of not less than 1.70, and a lens with a low refractive index is a lens with a refractive index of not more than 1.60.

[0055] In some embodiments, the fourth lens L4 is a biconcave negative lens, and the fifth lens L5 is a biconvex positive lens. The magnifying side and the reducing side of the fourth lens L4 are both concave. The magnifying side and the reducing side of the fifth lens L5 are both convex.

[0056] In some embodiments, the sixth lens L6 is a biconvex positive lens, the seventh lens L7 is a biconcave negative lens, and the eighth lens L8 is a biconvex positive lens. The magnifying side and the reducing side of the sixth lens L6 are both convex. The magnifying side and the reducing side of the seventh lens L7 are both concave. The magnifying side and the reducing side of the eighth lens L8 are both convex.

[0057] In these embodiments, by reasonably setting the concave and convex shapes of each lens surface, the optical lens can have smaller aberrations, better light utilization, and higher resolution.

[0058] In some embodiments, the image plane height of the projection lens is H, the aperture number of the projection lens is Fno, and the outer diameter of the largest lens in the projection lens is L. MAX The projection lens satisfies at least one of the following relationships: 8 ≤ TTL / H ≤ 22; 10mm ≤ L MAX / Fno≤25mm.

[0059] The Fno parameter represents the light-gathering capability of a lens. Fno = focal length (EFL) of the projection lens / aperture diameter. With a constant focal length, a larger aperture diameter results in a smaller Fno value, stronger light-gathering capability, and higher brightness. The outer diameter of a lens can be understood as the length of the outer diameter of a circular object, that is, the longest straight-line distance from one edge of the lens to the other. It can also be understood as the diameter of the lens itself. Within a certain range of Fno, the maximum outer diameter of the lens is correspondingly limited, thus enabling the design of small projection lenses to reduce space occupation.

[0060] Optionally, the projection lens satisfies the following relationship: 8≤TTL / H≤22; 10mm≤L MAX / Fno≤25mm. While possessing strong light transmission capability, it also meets the characteristic of short lens length, which allows for the miniaturization of projection devices using this projection lens.

[0061] For example, L MAX The / Fno ratio can be 25mm, 24mm, 22mm, 20mm, 18mm, 16mm, 14mm, 12mm, 10mm, etc. L MAX The ratio / Fno can also be any combination of the above values. Optionally, the largest lens in the projection lens can be the first lens L1.

[0062] In some embodiments, the focal length of the first lens group G1 is EFL. ZOOM1 The focal length of the second lens group G2 is EFL. ZOOM2 And it satisfies the following relationship: -65.0 < EFL ZOOM1 / EFL < -30.0; 0.5 < EFL ZOOM2 / EFL < 2.5.

[0063] For example, EFL ZOOM1 The / EFL ratio can be -64, -60, -58, -55, -50, -45, -40, -35, or -32, etc. EFL ZOOM1 The / EFL ratio can also be any combination of the above values.

[0064] For example, EFL ZOOM2 The ratio of / EFL can be 2.48, 2.4, 2.3, 2.0, 1.8, 1.6, 1.5, 1.2, 1.0, 0.8, 0.7, or 0.6, etc. EFL ZOOM2 The / EFL ratio can also be any combination of the above values.

[0065] In some embodiments, the aperture number of the projection lens is Fno, and the projection lens satisfies the following relationship: Fno ≤ 2.8. The Fno parameter represents the light-gathering capability of the lens. Fno = focal length (EFL) of the projection lens / aperture diameter. With the focal length remaining constant, a larger aperture diameter results in a smaller Fno value, stronger light-gathering capability, and higher brightness. In this embodiment, the projection lens can increase the relative aperture of the stop S to achieve a large aperture, increase light transmission, and improve brightness.

[0066] For example, the aperture number Fno of the projection lens can be 1.5, 1.6, 1.8, 2.2, 2.4, 2.6, or 2.8, etc. Of course, the aperture number Fno of the projection lens can also be any combination of the above values.

[0067] In some embodiments, the projection lens satisfies the following relationship: 8mm≤EFL≤25mm.

[0068] For example, the focal length (EFL) of the projection lens can be 8mm, 9mm, 10mm, 12mm, 13mm, 15mm, 16mm, 18mm, 19mm, 21mm, 23mm, or 25mm, etc. The focal length (EFL) of the projection lens can also be any combination of the above values.

[0069] In some embodiments, the projection lens satisfies the following relationship: TTL≤180mm.

[0070] For example, the total optical length (TTL) of the projection lens can be 180mm, 179mm, 178mm, 177mm, 176mm, 175mm, 174mm, 173mm, 172mm, 171mm, or 170mm, etc. Of course, the total optical length (TTL) of the projection lens can also be any combination of the above values.

[0071] In some embodiments, the projection lens satisfies the following relationship: BFL ≥ 20mm. BFL can be the distance from the tenth lens L10 to the DMD in the projection lens. The space between the tenth lens L10 and the DMD can be used to place the prism P, protective glass CG, etc.

[0072] For example, the back focal length (BFL) of the projection lens can be 20mm, 25mm, 30mm, 35mm, 40mm, 45mm, 50mm, 55mm, 60mm, 65mm, or 70mm, etc. Of course, the back focal length (BFL) of the projection lens can also be any combination of the above values.

[0073] In some embodiments, the diameter of each lens is no greater than 50 mm. This facilitates the miniaturization of the projection lens. For example, the diameter of each lens can be 50 mm, 48 mm, 45 mm, 40 mm, 38 mm, 36 mm, 35 mm, 34.6 mm, 34.4 mm, 34.2 mm, or 34.0 mm, etc. Of course, the diameter of each lens can also be any combination of the above values.

[0074] In some embodiments, the projection lens uses all-glass spherical lenses. An all-glass spherical lens is a lens whose front and back surfaces are both spherical, or one surface is spherical and the other is flat, and the entire lens is made of glass. Since the radius of curvature is the same in all directions, the refractive power is also equal.

[0075] In these embodiments, the projection lens uses all-glass spherical lenses, without plastic aspherical lenses or glass molded aspherical lenses, which greatly reduces the overall lens cost and manufacturing difficulty.

[0076] In some embodiments, the second lens group G2 includes at least two lenses with a refractive index greater than 1.8. This can correct lens distortion and astigmatism, and also correct the sine difference of the lens to a certain extent, thereby further improving image quality. For example, the second lens group G2 may include 2, 3, 4, 5, or 6 lenses with a refractive index greater than 1.8.

[0077] In some embodiments, the second lens group G2 includes X lenses whose refractive index temperature coefficient Dn / Dt is negatively proportional to their focal length EFFL-n, i.e., (Dn / Dt) / EFFL-n < 0, where Dn / Dt is the refractive index temperature coefficient of the lens, and EFFL-n is the focal length of the lens. Furthermore, the following relationship is satisfied: 1 ≤ X ≤ 4. A lens with positive refractive power and a negative refractive index temperature coefficient Dn / Dt can compensate for thermal defocusing of the entire projection lens. A lens with negative refractive power and a positive refractive index temperature coefficient Dn / Dt can also compensate for thermal defocusing of the entire projection lens.

[0078] Optionally, X can be 1, 2, 3, or 4. For example, the ratio of the refractive index temperature coefficient to the focal length of the sixth lens L6 can be negative; the ratio of the refractive index temperature coefficient to the focal length of the eighth lens L8 can be negative; and the ratio of the refractive index temperature coefficient to the focal length of the tenth lens L10 can be negative.

[0079] In these embodiments, the projection lens that meets the above conditions can effectively compensate for thermal defocusing, so that the projection lens does not have a significant impact on image quality within a certain temperature range.

[0080] The projection lens provided in this application has a precise structure, enabling a low-cost, compact design. The lens is small in size, with significant limitations on its overall length and lens aperture to minimize space occupation. The compact structural design allows for miniaturization of the projection lens. It satisfies the requirements of high resolution while maintaining a compact structure and controllable cost. When applied to automotive applications, it provides greater design freedom to avoid interference issues caused by interior trim components. This application is based on optical imaging principles, using optical design software to repeatedly optimize the curvature radius, material, thickness, air gap, and two cemented lenses of the projection lens. This achieves the goals of low aberration, high resolution, long back focal length, small overall length, simple structure, high manufacturability, and ease of mass production.

[0081] A second aspect of this application also provides a projection system, which includes a projection lens according to any embodiment of the first aspect described above. Since the projection system of this application includes a projection lens according to any embodiment of the first aspect described above, it also possesses the aforementioned advantages of the projection lens of this application.

[0082] A third aspect of this application also provides a projection device, which includes a projection lens of any embodiment of the first aspect or a projection system of the second aspect. Since the projection device of this application includes a projection lens of any embodiment of the first aspect or a projection system of the second aspect, it also possesses the aforementioned advantages of the projection lens of this application.

[0083] The technical solution of this application will be further described below with reference to the embodiments.

[0084] Example 1

[0085] Please refer to the following: Figure 1 The projection lens in Embodiment 1, from the magnification side to the reduction side, includes, in sequence, a first lens L1, a second lens L2, an eleventh lens L11, a third lens L3, a fourth lens L4, a fifth lens L5, an aperture S, a twelfth lens L12, a sixth lens L6, a seventh lens L7, an eighth lens L8, a ninth lens L9, a tenth lens L10, a prism P, and a protective glass CG.

[0086] The lens consists of the following lenses: Lens 1 (L1) is a meniscus negative lens with its convex surface facing the magnifying side; Lens 2 (L2) is a meniscus positive lens with its convex surface facing the magnifying side; Lens 11 (L11) is a meniscus negative lens with its convex surface facing the magnifying side; Lens 3 (L3) is a meniscus negative lens with its convex surface facing the magnifying side; Lens 4 (L4) is a biconcave negative lens; Lens 5 (L5) is a biconvex positive lens; Lens 12 (L12) is a meniscus negative lens with its convex surface facing the magnifying side; Lens 6 (L6) is a biconvex positive lens; Lens 7 (L7) is a biconcave negative lens; Lens 8 (L8) is a biconvex positive lens; Lens 9 (L9) is a plano-convex positive lens, with its magnifying side being planar and its reducing side being convex; and Lens 10 (L10) is a biconvex positive lens. The overall optical power of the lens is positive.

[0087] The relevant parameters of each component are shown in Table 1.

[0088] Table 1

[0089]

[0090]

[0091] Among them, surfaces 1 to 26 are arranged sequentially from the enlarged side to the reduced side.

[0092] Example 1 provides a long back focal length (BFL) projection lens with a back focal length (BFL) of 26.9mm, a BFL / EFL ratio of 1.92, and a BFL / TTL ratio of 0.3. This lens has a precise structure, achieving a low-cost, compact imaging lens. This application is based on optical imaging principles, using optical design software to repeatedly optimize the curvature radius, material, thickness, air gap, and two cemented lenses of the projection lens, achieving low aberrations, high resolution, long back focal length, small overall length, simple structure, high manufacturability, and ease of mass production.

[0093] Example 2

[0094] Please refer to the following: Figure 2 The projection lens in Embodiment 2, from the magnification side to the reduction side, includes, in sequence, a first lens L1, a second lens L2, an eleventh lens L11, a third lens L3, a fourth lens L4, a fifth lens L5, an aperture S, a twelfth lens L12, a sixth lens L6, a seventh lens L7, an eighth lens L8, a ninth lens L9, a tenth lens L10, a prism P, and a protective glass CG.

[0095] The difference between Example 2 and Example 1 is that the second lens L2 is a plano-convex positive lens, with a convex side for magnification and a flat side for reduction; the ninth lens L9 is a biconvex positive lens. The specific parameters of the projection lens are also different.

[0096] The relevant parameters of each component are shown in Table 2.

[0097] Table 2

[0098]

[0099] Among them, surfaces 1 to 26 are arranged sequentially from the enlarged side to the reduced side.

[0100] Example 2 provides a long back focal length (BFL) projection lens with a back focal length (BFL) of 26.9mm, a BFL / EFL ratio of 1.95, and a BFL / TTL ratio of 0.3. This lens has a precise structure, achieving a low-cost, compact imaging lens. This application is based on optical imaging principles, using optical design software to repeatedly optimize the curvature radius, material, thickness, air gap, and two cemented lenses of the projection lens, achieving low aberrations, high resolution, long back focal length, small overall length, simple structure, high manufacturability, and ease of mass production.

[0101] Example 3

[0102] Please refer to the following: Figure 3 The projection lens in Embodiment 3, from the magnification side to the reduction side, includes a first lens L1, a second lens L2, an eleventh lens L11, a third lens L3, a fourth lens L4, a fifth lens L5, an aperture S, a twelfth lens L12, a sixth lens L6, a seventh lens L7, an eighth lens L8, a ninth lens L9, a tenth lens L10, a prism P, and a protective glass CG.

[0103] The difference between Example 3 and Example 1 is that the ninth lens L9 is a meniscus lens with its convex surface facing the reduction side. Also, the specific parameters of the projection lens are different.

[0104] The relevant parameters of each component are shown in Table 3.

[0105] Table 3

[0106]

[0107] Among them, surfaces 1 to 26 are arranged sequentially from the enlarged side to the reduced side.

[0108] Example 3 provides a long back focal length (BFL) projection lens with a back focal length (BFL) of 28.7mm, a BFL / EFL ratio of 2.11, and a BFL / TTL ratio of 0.32. This lens has a precise structure, achieving a low-cost, compact imaging lens. This application is based on optical imaging principles and uses optical design software to repeatedly optimize the curvature radius, material, thickness, air gap, and two cemented lenses of the projection lens, achieving low aberrations, high resolution, long back focal length, small overall length, simple structure, high manufacturability, and ease of mass production.

[0109] This application may be implemented in other specific forms without departing from its spirit and essential characteristics. For example, the algorithm described in a particular embodiment may be modified without departing from the basic spirit of this application. Therefore, the present embodiments are to be regarded as exemplary rather than limiting in all respects, and the scope of this application is defined by the appended claims rather than the foregoing description, and all changes falling within the meaning and scope of the claims and their equivalents are thus included within the scope of this application.

Claims

1. A projection lens, characterized in that, Along the optical axis from the magnifying side to the reducing side, it includes a first lens group with negative optical power, an aperture, and a second lens group with positive optical power in sequence. The first lens group includes a first lens, a second lens, a third lens, a fourth lens, and a fifth lens arranged sequentially along the optical axis from the magnification side to the reduction side. The first lens has negative refractive power, the second lens has positive refractive power, the third lens has negative refractive power, the fourth lens has negative refractive power, and the fifth lens has positive refractive power. The second lens group includes a sixth lens, a seventh lens, an eighth lens, a ninth lens, and a tenth lens arranged sequentially along the optical axis from the magnification side to the reduction side. The sixth lens has positive refractive power, the seventh lens has negative refractive power, the eighth lens has positive refractive power, the ninth lens has positive refractive power, and the tenth lens has positive refractive power. The projection lens has a focal length of EFL, a back focal length of BFL, and a total optical length of TTL. The projection lens satisfies at least one of the following conditions: 1.6 ≤ BFL / EFL ≤ 2.5; BFL / TTL≥0.

3.

2. The projection lens according to claim 1, characterized in that, The first lens group further includes an eleventh lens, which is disposed between the second lens and the third lens, and the eleventh lens has negative refractive power; and / or, The second lens group also includes a twelfth lens, which is disposed between the aperture stop and the eighth lens, and the twelfth lens has negative refractive power.

3. The projection lens according to claim 1, characterized in that, The fourth lens and the fifth lens form a cemented doublet with positive refractive power; and / or, The sixth lens, the seventh lens, and the eighth lens together form a triplex lens group with positive refractive power.

4. The projection lens according to claim 3, characterized in that, The refractive index of the fourth lens is less than that of the fifth lens; and / or, The refractive indices of the sixth lens and the eighth lens are both less than that of the seventh lens.

5. The projection lens according to claim 3, characterized in that, The fourth lens is a biconcave negative lens, and the fifth lens is a biconvex positive lens; and / or, The sixth lens is a biconvex positive lens, the seventh lens is a biconcave negative lens, and the eighth lens is a biconvex positive lens.

6. The projection lens according to claim 1, characterized in that, The image plane height of the projection lens is H, the aperture number of the projection lens is Fno, and the outer diameter of the largest lens in the projection lens is L. MAX The projection lens satisfies at least one of the following relationships: 8≤TTL / H≤22; 10mm≤L MAX / Fno≤25mm。 7. The projection lens according to claim 1, characterized in that, The focal length of the projection lens is EFL, and the focal length of the first lens group is EFL. ZOOM1 The focal length of the second lens group is EFL. ZOOM2 And satisfy the following relation: -65.0<EFL ZOOM1 / EFL<-30.0; 0.5<EFL ZOOM2 / EFL<2.5。 8. The projection lens according to any one of claims 1 to 7, characterized in that, The aperture number of the projection lens is Fno, and the projection lens satisfies at least one of the following relationships: 8mm≤EFL≤25mm; TTL≤180mm; BFL ≥ 20mm; Fno≤2.8; The diameter of each lens shall not exceed 50mm.

9. The projection lens according to any one of claims 1 to 7, characterized in that, All projection lenses are all-glass spherical lenses.

10. The projection lens according to any one of claims 1 to 7, characterized in that, The second lens group includes at least two lenses with a refractive index greater than 1.8; and / or, The second lens group includes lenses with a negative ratio of refractive index temperature coefficient to focal length, and satisfies the following relationship: 1≤X≤4.

11. A projection system, characterized in that, Includes the projection lens according to any one of claims 1 to 10.

12. A projection device, characterized in that, Includes the projection lens of any one of claims 1 to 10 or the projection system of claim 11.

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