Projection lens and projection device

Abstract

Provided in the embodiments of the present application are a projection lens and a projection device. The projection lens sequentially comprises, from a projection side to an image source along the same optical axis, a first lens group, a second lens group, a third lens group and a fourth lens group, wherein at least two of the first lens group, the second lens group and the third lens group are zoom groups; the zoom groups are movable along the optical axis so as to change the focal length of the projection lens; and the fourth lens group is movable along the optical axis, or the fourth lens group is a fixedly arranged lens group. When the zoom group having the longest moving distance among the zoom groups moves towards the projection side and reaches a first position, the projection lens switches to a telephoto mode. When the zoom group having the longest moving distance among the zoom groups moves towards the image source and reaches a second position, the projection lens switches to a wide-angle mode. The overall architecture of the projection lens of the present application has relatively low complexity and is relatively compact, such that the size of the projection lens can be reduced.

Description

Projection lens and projection equipment Technical Field

[0001] This application belongs to the field of projection imaging technology, and in particular relates to a projection lens and projection device. Background Technology

[0002] Zoom projection lenses can project images of different sizes in a fixed space. They are flexible and portable, and are widely used in home, office and other fields.

[0003] In related technologies, in order to meet users' demand for high performance (such as high brightness and high contrast) of projection lenses, zoom lenses often use more lenses and have a larger lens size. This not only increases the cost of the lens, but also affects the flexibility and portability of the lens. Summary of the Invention

[0004] This application provides a projection lens and projection device with low overall architectural complexity and a compact design, enabling a reduction in the size of the projection lens and achieving miniaturization. Furthermore, this projection lens exhibits low distortion, good imaging performance, and low cost.

[0005] In a first aspect, embodiments of this application provide a projection lens, which comprises, along the same optical axis from the projection side to the image source, a first lens group, a second lens group, a third lens group, and a fourth lens group. At least two of the first, second, and third lens groups are zoom groups, which can move along the optical axis to change the focal length of the projection lens. The fourth lens group can move along the optical axis, or it can be a fixed lens group. Among these, the zoom group that moves the longest distance moves towards the projection side, and when it reaches a first position, the projection lens switches to telephoto mode. When the zoom group that moves the longest distance moves towards the image source, and when it reaches a second position, the projection lens switches to wide-angle mode.

[0006] This application provides a projection lens in which at least two of the first, second, and third lens groups are zoom groups. This allows for three-element or two-element zoom, resulting in a lower overall structural complexity and a more compact design, thus reducing the size of the projection lens and achieving miniaturization. Furthermore, this projection lens exhibits low distortion, good imaging performance, and low cost.

[0007] For example, the first lens group, the second lens group, and the third lens group are all zoom groups; wherein, the fourth lens group is a fixed lens group, and the first lens group can move along the optical axis for focusing; or, the fourth lens group can move along the optical axis for focusing.

[0008] For example, the second and third lens groups are zoom groups; wherein the fourth lens group is a fixed lens group, and the first lens group can move along the optical axis for focusing; or, the first lens group is a fixed lens group, and the fourth lens group can move along the optical axis for focusing.

[0009] The projection lens provided in this embodiment employs a three-element zoom or a two-element zoom, which can effectively reduce the number of structural groups and lower the complexity of the projection lens. Furthermore, the use of front-group zoom reduces design difficulty and lowers the cost of the projection lens.

[0010] For example, the first lens group includes a first lens, a second lens, and a third lens; wherein the first lens has negative optical power; the second lens has negative optical power; the third lens has positive optical power; the second lens group has positive optical power; and the third lens group includes at least one set of cemented lenses, and the cemented lenses have either positive or negative optical power.

[0011] In this embodiment, both the first and second lenses have negative optical power, which expand the field of view and correct distortion. The second lens group has positive optical power, which helps to collect light and makes the light path smoother, better correcting spherical aberration and astigmatism. It also effectively controls the front group aperture, improving the overall lens size and diameter. The third lens group includes at least one set of cemented lenses, which effectively corrects chromatic aberration and spherical aberration.

[0012] For example, the first lens group includes at least one aspherical lens; and / or, the refractive index of at least one lens in the first lens group is greater than or equal to 1.7; and / or, the first lens is an aspherical lens; and / or, the refractive index of the third lens is greater than or equal to 1.7; and / or, the refractive index of at least one lens in the second lens group is greater than or equal to 1.7; and / or, the refractive index of at least one lens in the third lens group is greater than or equal to 1.7; and / or, the Abbe number of at least one lens in the third lens group is greater than or equal to 70; and / or, the at least one lens in the third lens group is an aspherical lens; and / or, the cemented lens is composed of two or three lenses cemented together.

[0013] For example, the magnifying side surface of the first lens is convex, and the reducing side surface of the first lens is concave; the magnifying side surface of the second lens is concave, and the reducing side surface of the second lens is concave; the magnifying side surface of the third lens is convex, and the reducing side surface of the third lens is convex.

[0014] In this embodiment, the first lens group includes at least one aspherical lens to correct distortion and spherical aberration at large apertures, as well as off-axis aberrations such as coma, field curvature, and astigmatism. The third lens group has at least one low-dispersion lens to correct chromatic aberration. Furthermore, avoiding excessively high Abbe numbers for the low-dispersion lens in the third lens group helps prevent thermal expansion and makes it suitable for high-brightness scenes.

[0015] For example, the second lens group includes a fourth lens with a refractive index greater than or equal to 1.7; the third lens group includes a first cemented lens and an eighth lens; wherein the first cemented lens is formed by cementing a fifth lens and a sixth lens together, or by cementing a fifth lens, a sixth lens, and a seventh lens together; wherein the third lens group satisfies at least one of the following: the Abbe number of at least one lens in the first cemented lens is greater than or equal to 70; the refractive index of at least one lens in the first cemented lens is greater than or equal to 1.7; and the refractive index of the eighth lens is greater than or equal to 1.7.

[0016] For example, the magnifying side surface of the fourth lens is convex, and the reducing side surface of the fourth lens is either flat or concave; the magnifying side surface of the fifth lens is convex, and the reducing side surface of the fifth lens is convex; the magnifying side surface of the sixth lens is concave, and the reducing side surface of the sixth lens is concave; the magnifying side surface of the seventh lens is convex, and the reducing side surface of the seventh lens is convex; the magnifying side surface of the eighth lens is convex, and the reducing side surface of the eighth lens is convex.

[0017] In this embodiment, the fourth lens in the second lens group has positive optical power, which collects light and makes the light path smoother, thus better correcting spherical aberration and astigmatism. In the third lens group, a first cemented lens is used, and this first cemented lens has a lens with low dispersion, which can correct chromatic aberration and spherical aberration and improve brightness.

[0018] For example, the fourth lens group includes a ninth lens, the refractive index of the ninth lens is greater than or equal to 1.9, the magnifying side surface of the ninth lens is convex, and the reducing side surface of the ninth lens is either convex or concave.

[0019] In this embodiment, the fourth lens group can move along the optical axis, which can more effectively improve the resolution at different sizes. The fourth lens group uses lenses with a high refractive index, which can correct the telecentric angle, more effectively control the aperture, and thus reduce the size of the projection lens.

[0020] For example, the wide-angle focal length of the projection lens is Fs, which is the focal length of the projection lens in wide-angle mode; the effective focal length of the first lens group is F1, the effective focal length of the second lens group is F2, the effective focal length of the third lens group is F3, and the effective focal length of the fourth lens group is F4; wherein, the effective focal length F1 of the first lens group and the wide-angle focal length Fs satisfy: -5.6 < F1 / Fs < -1.0; the effective focal length F2 of the second lens group and the wide-angle focal length Fs satisfy: 0.6 < F2 / Fs < 6.3; the effective focal length F3 of the third lens group and the wide-angle focal length Fs satisfy: 4.0 < F3 / Fs < 9.6, or -70 < F3 / Fs < -120; the effective focal length F4 of the fourth lens group and the wide-angle focal length Fs satisfy: 0.5 < F4 / Fs < 5.1.

[0021] In this embodiment, the first lens group has a negative focal length, the second lens group has a positive focal length, the third lens group has a positive focal length, and the fourth lens group can also have a positive focal length. This enables three-element or two-element zoom, effectively reducing the number of structural groups and lowering the complexity of the projection lens. Furthermore, the use of front-group zoom reduces design difficulty and cost. Additionally, the negative focal length of the first lens group allows for control of the aperture and the lens's field of view, enabling diffused light at the wide-angle end of the projection lens.

[0022] For example, the zoom ratio of the projection lens is ZR, which is the ratio of the focal length at the telephoto end to the focal length at the wide-angle end of the projection lens. The focal length at the telephoto end is the focal length of the projection lens in telephoto mode, and the focal length at the wide-angle end is the focal length of the projection lens in wide-angle mode. The zoom ratio ZR and the wide-angle focal length Fs satisfy: 6.0 < Fs / ZR < 16.8. Furthermore, with a fixed zoom ratio ZR, a smaller wide-angle focal length Fs indicates a tendency towards a wide-angle and short-focal-length lens, significantly increasing design complexity. Conversely, with a fixed wide-angle focal length, a larger zoom ratio ZR indicates a larger projection size that the zoom lens can cover during zooming, also significantly increasing design complexity.

[0023] In this embodiment, a larger magnification can be achieved at the wide-angle end, thereby improving the imaging performance at the wide-angle end.

[0024] For example, the distance the second lens group moves along the optical axis is X2, the back focal length of the projection lens is BF, the back focal length is the distance on the optical axis between the reduced side surface of the designated lens and the image source, the designated lens is the lens in the projection lens that is closest to the image source, and the reduced side surface of the designated lens is the surface facing the image source; the total optical length at the wide-angle end of the projection lens is TTL, which is the total optical length of the projection lens in wide-angle mode; wherein, the distance X2 the second lens group moves along the optical axis and the total optical length TTL at the wide-angle end satisfy: 0≤X2 / TTL≤0.3; the back focal length BF of the projection lens and the total optical length TTL at the wide-angle end satisfy: 0.1≤BF / TTL.

[0025] In this embodiment, despite the limited overall optical length of the projection lens, a relatively long back focal length is achieved, which presents a significant design challenge but also results in superior imaging performance. Furthermore, while the overall optical length of the projection lens is limited, the movable distance of the front lens group (such as the second lens group) is relatively long, leading to a large magnification ratio for the projection lens, which, while challenging to design, also contributes to excellent imaging performance.

[0026] For example, the aperture number of the projection lens is F. NO The projection lens has a back focal length of BF, which is the distance on the optical axis between the reduced-size surface of the designated lens and the image source. The designated lens is the lens closest to the image source in the projection lens. The projection lens has a first aperture of Φ1 and a second aperture of Φ2. The first aperture is the aperture of the lens closest to the projection side in the projection lens, and the second aperture is the aperture of the designated lens. The aperture number F... NO Satisfy: 1.5≤F NO ≤3.0; First aperture Φ1 and aperture number F NO Satisfies: 6.6≤Φ1 / F NO ≤40; The second aperture Φ2 and the back focal length BF of the projection lens satisfy: 0.5≤Φ2 / BF≤1.7.

[0027] The projection lens provided in this embodiment has a large aperture number, enabling it to receive more light. In this embodiment, the ratio of the first aperture to the aperture number and the ratio of the second aperture to the back focal length satisfy the above conditions, ensuring that the projection lens can collect more light while maintaining a small size, resulting in a significant increase in brightness.

[0028] For example, the projection lens also includes an aperture stop located between the second lens group and the third lens group. The aperture stop moves along the optical axis as the third lens group moves. The distance between the aperture stop and a designated lens is STL, where the designated lens is the lens closest to the image source in the projection lens. The rear group focal length of the projection lens is FL, which is the effective focal length of the rear group of lenses, including the third and fourth lens groups. The STL and the rear group focal length FL satisfy: -5.0 ≤ STL / FL ≤ 6.0.

[0029] In the projection lens provided in this embodiment, the aperture stop is close to the rear lens group, which is difficult to design, but can reduce the total optical length of the projection lens and reduce the size of the lens.

[0030] For example, the effective focal length of the projection lens is F, and the image plane height of the projection lens is H. image Among them, the effective focal length F of the projection lens and the image plane height H of the projection lens are... image Satisfies: 1.4≤F / H image ≤2.4.

[0031] In this embodiment, the effective focal length and image plane height of the projection lens meet the corresponding conditions, enabling the use of fewer lenses to obtain a larger focal length. This design is challenging but helps to reduce the size of the projection lens.

[0032] Secondly, embodiments of this application provide a projection device, including: a housing; and a projection lens as described in the first aspect of embodiments of this application, the projection lens being disposed in the housing. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 is a schematic diagram of a projection lens provided in an embodiment of this application;

[0035] Figure 2 is a modulation transfer function diagram of the projection lens provided in an embodiment of this application;

[0036] Figure 3 is a distortion diagram of the projection lens provided in an embodiment of this application;

[0037] Figure 4 is a dot matrix diagram of the projection lens provided in an embodiment of this application;

[0038] Figure 5 is a schematic diagram of another projection lens provided in an embodiment of this application;

[0039] Figure 6 is a schematic diagram of another projection lens provided in an embodiment of this application.

[0040] Explanation of reference numerals in the attached figures: 10, First lens group; 11, First lens; 12, Second lens; 13, Third lens; 20, Second lens group; 21, Fourth lens; 30, Third lens group; 31, Fifth lens; 32, Sixth lens; 33, Seventh lens; 34, Eighth lens; 35, Tenth lens; 40, Fourth lens group; 41, Ninth lens; 50, Stop; 60, Galvanometer (T); 70, Prism; 80, Light transmission protection device; 90, Image source. Detailed Implementation

[0041] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of this application. However, those skilled in the art will understand that this application may also be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods have been omitted so as not to obscure the description of this application with unnecessary detail.

[0042] It should be understood that, when used in this application specification and the appended claims, the term "comprising" indicates the presence of the described features, integrals, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or a collection thereof.

[0043] It should also be understood that the term “and / or” as used in this application specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0044] As used in this application specification and the appended claims, the term "if" may be interpreted, depending on the context, as "when," "once," "in response to determination," or "in response to detection." Similarly, the phrase "if determined" or "if detected [the described condition or event]" may be interpreted, depending on the context, as meaning "once determined," "in response to determination," "once detected [the described condition or event]," or "in response to detection [the described condition or event]."

[0045] Furthermore, in the description of this application and the appended claims, the terms "first," "second," "third," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0046] References to "one embodiment" or "some embodiments" as described in this specification mean that one or more embodiments of this application include a specific feature, structure, or characteristic described in connection with that embodiment. Therefore, the phrases "in one embodiment," "in some embodiments," "in other embodiments," "in still other embodiments," etc., appearing in different parts of this specification do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized. The terms "comprising," "including," "having," and variations thereof mean "including but not limited to," unless otherwise specifically emphasized.

[0047] This application provides a projection lens in which at least two of the first, second, and third lens groups are zoom groups. This allows for three-element or two-element zoom, resulting in a lower overall structural complexity and a more compact design, thus reducing the size of the projection lens and achieving miniaturization. Furthermore, this projection lens exhibits low distortion, good imaging performance, and low cost.

[0048] The projection lens of the present application embodiment will be further described in detail below with reference to the accompanying drawings.

[0049] Figure 1 is a schematic diagram of a projection lens provided in an embodiment of this application. As shown in Figure 1, the projection lens includes, along the same optical axis from the projection side (i.e., SCN) to the image source 90, a first lens group 10, a second lens group 20, a third lens group 30, and a fourth lens group 40. At least two of the first lens group 10, the second lens group 20, and the third lens group 30 are zoom groups, which can move along the optical axis to change the focal length of the projection lens. The fourth lens group 40 can move along the optical axis, or the fourth lens group 40 is a fixed lens group (for ease of explanation, it can be simply referred to as the fixed group).

[0050] Specifically, when the zoom group moves along the optical axis to the projection side, the projection lens switches to telephoto mode. When the zoom group moves along the optical axis to the image source 90, the projection lens switches to wide-angle mode. In particular, the zoom group that moves the longest distance among at least two zoom groups (also called the main zoom group) moves towards the projection side, and when it reaches the first position, the projection lens switches to telephoto mode; when the zoom group that moves the longest distance among at least two zoom groups moves towards the image source 90, and when it reaches the second position, the projection lens switches to wide-angle mode.

[0051] This application provides a projection lens in which at least two of the first, second, and third lens groups are zoom groups. This allows for three-element or two-element zoom, resulting in a lower overall structural complexity and a more compact design, thus reducing the size of the projection lens and achieving miniaturization. Furthermore, this projection lens exhibits low distortion, good imaging performance, and low cost.

[0052] In this embodiment, as shown in FIG1, the projection lens further includes an aperture stop (i.e., STOP) 50, which is located between the second lens group 20 and the third lens group 30. When the third lens group 30 moves along the optical axis, the aperture stop moves with the third lens group 30.

[0053] In some embodiments, as shown in FIG1, the projection lens further includes an image source 90. Exemplarily, the image source 90 may be a Digital Micromirror Device (DMD) chip. A DMD chip consists of multiple digital micromirrors arranged in a matrix. During operation, each micromirror can deflect and lock in both directions, thereby projecting light in a predetermined direction and oscillating at a frequency of tens of thousands of hertz. The light beam from the illumination source is reflected by the flipping of the micromirrors into the optical system and imaged on the screen. DMD chips have advantages such as high resolution and no need for digital-to-analog conversion of the signal. Exemplarily, the image source 90 may also be a Liquid Crystal on Silicon (LCOS) chip or other display elements that can be used to emit light; this application does not limit this choice.

[0054] In some embodiments, as shown in FIG1, the projection lens further includes a galvanometer (which may be represented as T) 60, a prism (which may be represented as P) 70, and a light-transmitting protection device (which may be represented as CG) 80. The galvanometer 60 can improve the resolution of the image output by the image source 90. The prism 70 is used with the image source 90 in conjunction with the projection lens and propagates the corresponding projection light to the lens group for subsequent display of the projected image. The light-transmitting protection device 80 can be a transparent glass plate. For example, the transparent glass plate can be placed over the light-emitting surface of the image source 90, effectively protecting the image source 80 and preventing external dust from entering the image source 90 while ensuring good light transmittance.

[0055] In this embodiment, at least two of the first lens group 10, the second lens group 20, and the third lens group 30 are zoom groups; the fourth lens group 40 is either a movable group (i.e., the fourth lens group 40 can move along the optical axis) or a fixed group. That is, the projection lens can be a three-element zoom or a two-element zoom. Furthermore, either the first lens group 10 or the fourth lens group 40 has a focusing function. The projection lens provided in this embodiment, employing a three-element or two-element zoom, can effectively reduce the number of structural groups and lower the complexity of the projection lens. Moreover, the use of front-group zoom in this projection lens reduces design difficulty and lowers the cost of the projection lens.

[0056] In some examples, taking a three-element zoom projection lens as an example, the first lens group 10, the second lens group 20, and the third lens group 30 are all zoom groups, while the fourth lens group 40 is a moving group. In this architecture, when the fourth lens group 40 is in the moving group, it is used for focusing. It can be understood that the zoom mechanism of this architecture is an optically non-homofocal zoom mechanism. In this architecture, the fourth lens group 40 can move relative to the image plane, reducing the number of other structural components and thus reducing the size of the projection lens.

[0057] In some examples, taking a three-element zoom projection lens as an example, the first lens group 10, the second lens group 20, and the third lens group 30 are all zoom groups, while the fourth lens group 40 is a fixed group. In this architecture, the first lens group 10 moves along the optical axis to perform focusing. That is, the movement of the first lens group 10 along the optical axis achieves both zooming and focusing.

[0058] In some examples, taking a two-element zoom projection lens as an example, the second lens group 20 and the third lens group 30 are the zoom groups, while the fourth lens group 40 is the fixed group. In this architecture, the first lens group 10 can move along the optical axis to achieve focusing. That is, moving the first lens group 10 along the optical axis achieves both zooming and focusing. It can be understood that the zoom mechanism of this architecture is an optically parfocal zoom mechanism.

[0059] In some examples, taking a two-element zoom projection lens as an example, the second lens group 20 and the third lens group 30 are the zoom group, and the fourth lens group 40 is the moving group. In this architecture, when the fourth lens group 40 is in the moving group, it is used for focusing. This architecture allows the fourth lens group 40 to move relative to the image plane, reducing the number of other structural components and thus reducing the size of the projection lens.

[0060] The above describes the architecture of the projection lens provided in the embodiments of this application. The individual lens groups will now be described separately.

[0061] In some embodiments, the first lens group 10 includes at least one aspherical lens. For example, the first lens group 10 may include an aspherical lens. For instance, taking a first lens group 10 comprising a first lens, a second lens, and a third lens, the first lens is an aspherical lens.

[0062] For example, the first lens group 10 may include two aspherical lenses. For instance, continuing with the example of the first lens group 10 including a first lens, a second lens, and a third lens, both the first lens and the third lens are aspherical lenses.

[0063] In some embodiments, the surface profile data of an aspherical lens can be determined according to the following formula (1).

[0064] Where z is the surface elevation; c is the curvature; r is the radial radius; k is the quadratic coefficient; and α1 to α8 are the aspherical coefficients corresponding to the second to sixteenth orders.

[0065] For example, the aspherical lens here can be a glass aspherical lens or a plastic (or resin) aspherical lens. That is to say, in this embodiment, the material of the aspherical lens in the first lens group 10 is not specifically limited.

[0066] In this embodiment, by incorporating an aspherical lens in the first lens group 10, different viewing heights can be formed locally to correct the optical path, thereby correcting distortion and spherical aberration at large apertures, as well as off-axis aberrations such as coma, field curvature, and astigmatism. This ensures a relatively gentle angle of incidence between the light and the lens surface, facilitating processing and production. Furthermore, the first lens group 10 can also correct higher-order aberrations.

[0067] In some embodiments, at least one lens in the first lens group 10 has a refractive index greater than or equal to 1.7. For example, the first lens group 10 includes a lens with a refractive index greater than or equal to 1.7. Optionally, the first lens group 10 includes a lens with a refractive index greater than or equal to 1.8. For instance, continuing with the example of the first lens group 10 including a first lens, a second lens, and a third lens, the third lens has a refractive index of 1.9.

[0068] For example, continuing with the example of the first lens group 10 including a first lens, a second lens, and a third lens, the refractive index of the second lens is 1.51.

[0069] For example, the first lens group 10 includes two lenses with a refractive index greater than or equal to 1.7. For instance, continuing with the example of the first lens group 10 including a first lens, a second lens, and a third lens, the second lens has a refractive index of 1.48, and the third lens has a refractive index of 1.9.

[0070] In this embodiment, the second lens group 20 serves as a receiver, used to transmit light. In some embodiments, the second lens group 20 has positive optical power. Optionally, the second lens group 20 may include at least one lens with positive optical power.

[0071] For example, the second lens group 20 includes a lens with positive optical power. For instance, the second lens group 20 may include a fourth lens with positive optical power. Alternatively, the second lens group 20 may include a cemented doublet lens, in which one lens has positive optical power and at least one lens has a refractive index greater than 1.7 and at least one lens has an Abbe number greater than 50.

[0072] For example, when the second lens group 20 includes at least two lenses, the second lens group 20 may include two lenses with positive optical power.

[0073] In this way, by using a lens with positive optical power, light can be collected, resulting in a smooth transition of light throughout the optical path. This effectively controls the front aperture of the projection lens, thereby reducing its size. Furthermore, the second lens group 20 can also effectively control the light flux.

[0074] It should be noted that the front aperture of the projection lens can refer to the aperture of the first lens group.

[0075] The refractive index of at least one lens in the second lens group 20 is greater than or equal to 1.7. Optionally, the refractive index of at least one lens in the second lens group 20 is greater than or equal to 1.8.

[0076] For example, the second lens group 20 includes a lens with a refractive index greater than or equal to 1.7. For instance, if the second lens group 20 includes a fourth lens with a refractive index of 1.7, or if the second lens group 20 includes a fourth lens with a refractive index of 1.91, this is also an example.

[0077] In some embodiments, the second lens group 20 may further include at least one set of cemented lenses. For example, the cemented lens may be composed of two lenses cemented together or three lenses cemented together.

[0078] For example, the second lens group 20 may include a cemented doublet lens or a cemented triplet lens.

[0079] In this embodiment, by incorporating a cemented lens in the second lens group 20, the overall optical length of the projection lens can be reduced, which helps to shrink the size of the projection lens. Furthermore, the cemented lens can also correct chromatic aberration, eliminate spherical aberration, and improve the brightness of the projection lens.

[0080] In this embodiment, the third lens group 30 serves to correct chromatic aberration, spherical aberration, and higher-order aberrations.

[0081] In some embodiments, the third lens group 30 may include at least one set of cemented lenses, and the cemented lenses may have positive or negative optical power. For example, the cemented lens may be formed by cementing two lenses together, or by cementing three lenses together.

[0082] For example, the third lens group 30 may include a cemented triplet lens composed of a fifth lens, a sixth lens, and a seventh lens, as well as an eighth lens.

[0083] For example, the third lens group 30 may include a cemented triplet lens and a cemented doublet lens.

[0084] In this embodiment, by incorporating a cemented lens in the third lens group 30, the overall optical length of the projection lens can be reduced, which helps to shrink the size of the projection lens. Furthermore, the cemented lens can correct chromatic aberration and eliminate spherical aberration, while the cemented triplet lens can improve higher-order aberrations.

[0085] It should be noted that one of the lens groups, the second lens group 20 and the third lens group 30, has a cemented lens. For example, if the second lens group 20 has a cemented lens, then the third lens group 30 may not have a cemented lens. Conversely, if the third lens group 30 has a cemented lens, then the second lens group 20 may not have a cemented lens.

[0086] In some embodiments, at least one lens in the third lens group 30 has an Abbe number greater than or equal to 70.

[0087] For example, the third lens group 30 includes a lens with an Abbe number greater than or equal to 70. For instance, taking a third lens group 30 comprising a cemented triplet lens consisting of a fifth lens, a sixth lens, a seventh lens, and an eighth lens as an example, the Abbe number of the fifth lens is 95.

[0088] For example, continuing with the third lens group 30, which includes a cemented triplet lens consisting of a fifth lens, a sixth lens, and a seventh lens, as well as an eighth lens, the Abbe number of the seventh lens is 71.

[0089] Optionally, the third lens group 30 includes a lens with an Abbe number greater than or equal to 70 and an Abbe number less than or equal to 90. For example, continuing with the example of the third lens group 30 including a cemented triplet lens composed of a fifth lens, a sixth lens, a seventh lens, and an eighth lens, the Abbe number of the fifth lens is 80.

[0090] For example, the third lens group 30 includes two lenses with an Abbe number greater than or equal to 70. For instance, taking a third lens group 30 comprising a cemented triplet lens consisting of a fifth lens, a sixth lens, a seventh lens, and an eighth lens as an example, the Abbe number of the fifth lens is 95, and the Abbe number of the seventh lens is 71.

[0091] Optionally, the third lens group 30 includes two lenses with Abbe numbers greater than or equal to 70 and Abbe numbers less than or equal to 90. For example, continuing with the example of the third lens group 30 including a cemented triplet lens composed of a fifth lens, a sixth lens, and a seventh lens, and an eighth lens, the Abbe number of the fifth lens is 80, and the Abbe number of the seventh lens is 71.

[0092] In other words, the third lens group 30 has at least one low-dispersion lens, which can correct chromatic aberration. Furthermore, by avoiding excessively high Abbe numbers for the low-dispersion lenses in the third lens group 30, thermal expansion can be avoided, making it suitable for high-brightness scenes.

[0093] In some embodiments, at least one lens in the third lens group 30 has a refractive index greater than or equal to 1.7.

[0094] For example, the third lens group 30 includes a lens with a refractive index greater than or equal to 1.7. For instance, continuing with the example of the third lens group 30 including a cemented triplet lens composed of a fifth lens, a sixth lens, a seventh lens, and an eighth lens, the refractive index of the sixth lens is 1.74.

[0095] For example, the third lens group 30 includes two lenses with a refractive index greater than or equal to 1.7. For instance, continuing with the example of the third lens group 30 including a cemented triplet lens composed of a fifth lens, a sixth lens, a seventh lens, and an eighth lens, the refractive index of the sixth lens is 1.74 and the refractive index of the eighth lens is 1.8.

[0096] For example, taking the third lens group 30, which includes a cemented doublet consisting of a fifth lens and a sixth lens, and an eighth lens, as an example, the refractive index of the sixth lens is 1.74, and the refractive index of the eighth lens is 1.8.

[0097] For example, the third lens group 30 may also include multiple lenses with a refractive index greater than or equal to 1.7. For instance, continuing with the example of the third lens group 30 including a cemented triplet lens composed of a fifth lens, a sixth lens, and a seventh lens, and a cemented doublet lens composed of an eighth lens and a tenth lens, the refractive index of the fifth lens is 1.7, the refractive index of the sixth lens is 1.74, the refractive index of the eighth lens is 1.72, and the refractive index of the tenth lens is 1.8.

[0098] In some embodiments, the third lens group 30 may also include at least one aspherical lens.

[0099] For example, the third lens group 30 may also include an aspherical lens. For instance, continuing with the example of the third lens group 30 including a cemented triplet lens composed of a fifth lens, a sixth lens, a seventh lens, and an eighth lens, where the eighth lens is an aspherical lens.

[0100] In other words, at least one lens in the third lens group 30 can be an aspherical lens. This allows for the correction of distortion, field curvature, and spherical aberration, while also improving transmittance and brightness.

[0101] In some embodiments, at least one lens in the fourth lens group 40 has a refractive index greater than or equal to 1.9.

[0102] For example, the fourth lens group 40 includes a lens with a refractive index greater than or equal to 1.9. For instance, if the fourth lens group 40 includes a ninth lens, the refractive index of the ninth lens is 1.92. Also, continuing with the example of the fourth lens group 40 including a ninth lens, the refractive index of the ninth lens is 2.0.

[0103] In this embodiment, the fourth lens group uses a lens with a higher refractive index. This allows for correction of the telecentric angle, more effective control of the aperture, and thus a reduction in the size of the projection lens. Furthermore, using a lens with a higher refractive index in the fourth lens group also helps improve the edge performance of the lens and reduces the cost of the projection lens.

[0104] The above provides a detailed description of each lens group in the projection lens provided in the embodiments of this application. The parameters of the projection lens will now be explained.

[0105] In some embodiments, the projection lens satisfies the following conditions: -5.6 < F1 / Fs < -1.0; 0.6 < F2 / Fs < 6.3;

[0106] 4.0 < F3 / Fs < 9.6, or -120 < F3 / Fs < -70; 0.5 < F4 / Fs < 5.1.

[0107] For example, F1 / Fs can be -2.6, F2 / Fs can be 3.3, F3 / Fs can be 7.6, and F4 / Fs can be 3.1.

[0108] Wherein, F1 is the effective focal length of the first lens group 10, which is the distance between the front principal point (i.e., the reference point where light enters the lens group) of the first lens group 10 and the focal point. F2 is the effective focal length of the second lens group 20, which is the distance between the front principal point of the second lens group 20 and the focal point. F3 is the effective focal length of the third lens group 30, which is the distance between the front principal point of the third lens group 30 and the focal point. F4 is the effective focal length of the fourth lens group 40, which is the distance between the front principal point of the fourth lens group 40 and the focal point. Fs is the wide-angle focal length of the projection lens, which is the focal length of the projection lens in wide-angle mode, that is, the distance from the front principal point (i.e., the reference point where light enters the projection lens group) of the projection lens to the image source when the projection lens is in wide-angle mode.

[0109] In some examples, the projection lens satisfies the following condition: -2.5 <F1 / Fs<﹣2.3; 2.6<F2 / Fs<3.3; 6.0<F3 / Fs<7.6; 2.5<F4 / Fs<3.1。

[0110] For example, F1 / Fs can be -2.4, F2 / Fs can be 2.9, F3 / Fs can be 6.8, and F4 / Fs can be 2.8.

[0111] In some examples, the projection lens satisfies the following condition: -2.8 <F1 / Fs<﹣2.2; 2.9<F2 / Fs<3.8; 6.6<F3 / Fs<8.4; 2.3<F4 / Fs<2.9。

[0112] For example, F1 / Fs can be -2.6, F2 / Fs can be 3.3, F3 / Fs can be 7.8, and F4 / Fs can be 2.5.

[0113] In some examples, the projection lens satisfies the following condition: -2.7 <F1 / Fs<﹣2.0; 2.2<F2 / Fs<2.8; ﹣104<F3 / Fs<﹣83; 2.0<F4 / Fs<2.5。

[0114] For example, F1 / Fs can be -2.3, F2 / Fs can be 2.5, F3 / Fs can be -103, and F4 / Fs can be 2.2.

[0115] In this embodiment, the first lens group has a negative focal length, the second lens group has a positive focal length, the third lens group has a positive focal length, and the fourth lens group can also have a positive focal length. This enables three-element or two-element zoom, effectively reducing the number of structural groups and lowering the complexity of the projection lens. Furthermore, the use of front-group zoom reduces design difficulty and cost. Additionally, the negative focal length of the first lens group allows for control of the aperture and the lens's field of view, enabling diffused light at the wide-angle end of the projection lens.

[0116] In some embodiments, the zoom ratio ZR of the projection lens and the wide-angle focal length Fs of the projection lens satisfy: 6.0 < Fs / ZR < 16.8. Here, the zoom ratio ZR is the ratio of the telephoto focal length to the wide-angle focal length of the projection lens. The telephoto focal length is the focal length of the projection lens in telephoto mode, which is the distance from the front principal point of the projection lens to the image source when the projection lens is in telephoto mode.

[0117] In some examples, the zoom ratio ZR satisfies the following condition with respect to the wide-angle focal length Fs of the projection lens: 10 < Fs / ZR < 12.7.

[0118] For example, Fs / ZR can be 11.5.

[0119] In some examples, the zoom ratio ZR and the wide-angle focal length Fs of the projection lens satisfy the condition: 6.3 < Fs / ZR < 13.

[0120] For example, Fs / ZR can be 9.7.

[0121] In some examples, the zoom ratio ZR and the wide-angle focal length Fs of the projection lens satisfy the condition: 6.0 < Fs / ZR < 16.

[0122] For example, Fs / ZR can be 12.

[0123] Furthermore, with a fixed zoom ratio ZR, a smaller focal length Fs at the wide-angle end indicates a tendency towards a wide-angle and short-focal-length lens, significantly increasing design complexity. Conversely, with a fixed focal length at the wide-angle end, a larger zoom ratio ZR indicates a larger projection size that the zoom lens can cover during zooming, also significantly increasing design complexity. The projection lens provided in this embodiment achieves a larger magnification at the wide-angle end, improving imaging performance at that end.

[0124] In some embodiments, the projection lens satisfies the following conditions: 0≤X2 / TTL≤0.3; 0.1≤BF / TTL.

[0125] Where X2 is the distance the second lens group 20 moves along the optical axis; BF is the back focal length (also called back focal length or back focal length) of the projection lens, which is the distance on the optical axis between the reduced side surface of the specified lens and the image source, and the specified lens is the lens closest to the image source in the projection lens, that is, the last lens in the projection lens closest to the image source 90; TTL is the total optical length at the wide-angle end of the projection lens, which is the total optical length of the projection lens in wide-angle mode.

[0126] In some examples, the projection lens satisfies the following conditions: 0≤X2 / TTL≤0.1; 0.15≤BF / TTL.

[0127] For example, X2 / TTL can be 0; BF / TTL can be 0.16. For example, X2 / TTL can be 0.08; BF / TTL can be 0.3. For example, X2 / TTL can be 0.1; BF / TTL can be 0.15.

[0128] In some examples, the projection lens satisfies the following conditions: 0.1≤X2 / TTL≤0.26; 0.13≤BF / TTL.

[0129] For example, X2 / TTL can be 0.1; BF / TTL can be 0.2. For example, X2 / TTL can be 0.18; BF / TTL can be 0.26. For example, X2 / TTL can be 0.22; BF / TTL can be 0.13.

[0130] In some examples, the projection lens satisfies the following conditions: 0.1≤X2 / TTL≤0.3; 0.11≤BF / TTL.

[0131] For example, X2 / TTL can be 0.1; BF / TTL can be 0.2. For example, X2 / TTL can be 0.18; BF / TTL can be 0.3. For example, X2 / TTL can be 0.3; BF / TTL can be 0.11.

[0132] In this embodiment, the shorter the movable distance of the front lens group (such as the second lens group), the larger the proportion of the back focal length of the projection lens. Therefore, the projection lens provided in this embodiment, while limiting the total optical length of the projection lens, has a relatively long back focal length, which is challenging to design but results in better imaging performance. Furthermore, the longer movable distance of the front lens group (such as the second lens group) while limiting the total optical length of the projection lens allows for a larger magnification ratio, further enhancing the design challenge and resulting in better imaging performance.

[0133] In some embodiments, the projection lens satisfies the following condition: 1.5 ≤ F NO ≤3.0; 6.6≤Φ1 / F NO ≤40; 0.5≤Φ2 / BF≤1.7.

[0134] Among them, F NO Φ1 is the aperture number of the projection lens, which is the ratio of the effective focal length to the aperture diameter; BF is the back focal length of the projection lens; Φ1 is the first aperture of the projection lens, which is the aperture of the lens closest to the projection side, i.e., the aperture of the first lens closest to the projection side. Φ2 is the second aperture of the projection lens, which is the aperture of a designated lens in the projection lens. The designated lens is the lens closest to the image source in the projection lens, i.e., the last lens closest to the image source (such as the ninth lens 41).

[0135] It is understandable that the aperture of a lens can be either the diameter of the lens or the radius of the lens.

[0136] In some embodiments, the projection lens satisfies the following condition: 1.9 ≤ F NO ≤3.0; 12≤Φ1 / F NO ≤16; 0.5≤Φ2 / BF≤1.7.

[0137] For example, F NO 2.2 can be taken; Φ1 / F NO It can be taken as 14.4; Φ2 / BF can be taken as 0.47. For example, F NO 2.5 can be taken; Φ1 / F NO It can be 13; Φ2 / BF can be 1.2. For example, F NO 3.0 can be taken; Φ1 / F NO It can be 12; Φ2 / BF can be 1.7. For example, F... NO 3.0 can be taken; Φ1 / F NO Φ2 / BF can be taken as 16; Φ2 / BF can be taken as 1.5.

[0138] In some embodiments, the projection lens satisfies the following condition: 1.5 ≤ F NO ≤3.0; 10.2≤Φ1 / F NO ≤20.5; 0.7≤Φ2 / BF≤1.7.

[0139] For example, F NO 1.5 can be taken; Φ1 / F NO It can be 13; Φ2 / BF can be 0.8. For example, F NO 2.5 can be taken; Φ1 / F NOIt can be taken as 15; Φ2 / BF can be taken as 0.7. For example, F NO 3.0 can be taken; Φ1 / F NO It can be 18; Φ2 / BF can be 1.7. For example, F... NO 3.0 can be taken; Φ1 / F NO 20.5 can be taken; Φ2 / BF can be taken as 1.2.

[0140] In some embodiments, the projection lens satisfies the following condition: 1.7 ≤ F NO ≤3.0; 9.5≤Φ1 / F NO ≤25; 0.7≤Φ2 / BF≤1.7.

[0141] For example, F NO 1.7 can be taken; Φ1 / F NO It can be 13; Φ2 / BF can be 0.8. For example, F NO 2.5 can be taken; Φ1 / F NO 9.5 can be taken; Φ2 / BF can be taken as 0.7. For example, F NO 3.0 can be taken; Φ1 / F NO It can be 18; Φ2 / BF can be 1.7. For example, F... NO 3.0 can be taken; Φ1 / F NO 25 can be taken; Φ2 / BF can be taken as 1.2.

[0142] The projection lens provided in this embodiment has a large aperture number, enabling it to receive more light. In this embodiment, the ratio of the first aperture to the aperture number and the ratio of the second aperture to the back focal length satisfy the above conditions, ensuring that the projection lens can collect more light while maintaining a small size, resulting in a significant increase in brightness.

[0143] In some embodiments, the projection lens satisfies the following condition: -5.0 ≤ STL / FL ≤ 6.0.

[0144] Wherein, STL is the distance from the aperture stop to the designated lens, which is the lens in the projection lens that is closest to the image source, that is, the last lens in the projection lens that is closest to the image source 90; FL is the rear group focal length of the projection lens, which is the effective focal length of the rear group of the projection lens, including the third lens group 30 and the fourth lens group 40.

[0145] In some examples, the projection lens satisfies the following condition: 1.0 ≤ STL / FL ≤ 1.6.

[0146] For example, STL / FL can be 1.0. For example, STL / FL can be 1.3. For example, STL / FL can be 1.6.

[0147] In some examples, the projection lens satisfies the following condition: 1.1 ≤ STL / FL ≤ 1.4.

[0148] For example, STL / FL can be 1.1. For example, STL / FL can be 1.2. For example, STL / FL can be 1.4.

[0149] In the projection lens provided in this embodiment, the aperture stop is close to the rear lens group, which is difficult to design, but can reduce the total optical length of the projection lens and reduce the size of the lens.

[0150] In some embodiments, the effective focal length F of the projection lens and the image plane height H of the projection lens are... image Satisfies: 1.4≤F / H image ≤2.4. Wherein, the image plane height of the projection lens is the height dimension on the imaging plane, that is, 1 / 2 of the height of the image source.

[0151] For example, F / H image A value of 1.4 can be used. For example, F / H... image A value of 1.8 can be used. For example, F / H image 2.4 is acceptable.

[0152] In this embodiment, the greater the image plane height, the shorter the focal length of the projection lens. Based on this, the effective focal length of the projection lens and the image plane height in the projection lens provided in this embodiment meet the corresponding conditions, which can achieve a larger focal length with fewer lenses. The design is difficult, but it can help reduce the size of the projection lens.

[0153] In this embodiment, the Modulation Transfer Function (MTF) is a function that measures the contrast transfer capability of a projection lens at different spatial frequencies, reflecting the degree to which the projection lens retains object details. A higher MTF value indicates a stronger contrast transfer capability of the projection lens at that spatial frequency, and thus better preservation of image details.

[0154] Figure 2 is a modulation transfer function (MTF) diagram of the projection lens provided in this embodiment. As shown in Figure 2, the horizontal axis of the MTF is the spatial frequency (SRF) in cycles per mm, and the vertical axis is the OTF modulus. The projection lens provided in this embodiment maintains an OTF modulus of 0.6 or higher within the spatial frequency range of 0 mm to 93 mm, indicating high image quality and excellent image clarity. Therefore, the projection lens provided in this embodiment has good imaging performance.

[0155] Figure 3 is a distortion diagram of the projection lens provided in the embodiment of this application. As shown in Figure 3, the horizontal axis of the distortion diagram represents percentage (%), and the vertical axis represents the field of view. Distortion refers to the aberration caused by different magnifications of different parts of an object when it is imaged through a projection lens. Distortion can lead to a decrease in the similarity of the object and the image, but it does not affect the image sharpness. As shown in Figure 3, the distortion is less than 0.5% at the maximum field of view of 32.4°. Therefore, the projection lens provided in the embodiment of this application has low distortion.

[0156] Figure 4 is a dot matrix diagram of the projection lens provided in the embodiment of this application. As shown in Figure 4, it shows the size of the light spot under different fields of view (i.e., IMA). It can be seen that the projection lens provided in the embodiment of this application has a relatively concentrated light spot under different fields of view, such as a light spot smaller than 20μm, which has good imaging quality.

[0157] To further optimize the performance of the projection lens, four examples are used below.

[0158] Example 1

[0159] As shown in Figure 1, the projection lens, from the projection side to the image source 90 along the same optical axis, includes: a first lens 11, a second lens 12, a third lens 13, a fourth lens 21, an aperture 50, a fifth lens 31, a sixth lens 32, a seventh lens 33, an eighth lens 34, a ninth lens 41, a galvanometer (which can be represented as T) 60, a prism (which can be represented as P) 70, a light transmission protection device (which can be represented as CG) 80, and an image source 90.

[0160] The first lens 11, the second lens 12, and the third lens 13 constitute the first lens group 10. The first lens 11 has negative optical power; it is an aspherical lens with a radius of curvature of 25 mm on its magnifying side surface, which is convex, and a radius of curvature of 10 mm on its reducing side surface, which is concave. The second lens 12 has negative optical power; it is a spherical lens with a radius of curvature of -35 mm on its magnifying side surface, which is concave, and a radius of curvature of 40 mm on its reducing side surface, which is concave. The third lens 13 has positive optical power. It is a spherical lens with a radius of curvature of 95 mm on its magnifying side surface, which is convex, and a radius of curvature of -105 mm on its reducing side surface, which is convex. The refractive index of the third lens 13 is 1.9.

[0161] The fourth lens 21 forms part of the second lens group 20. The fourth lens 21 has positive optical power. The fourth lens 21 is a spherical lens with a radius of curvature of 45 mm on its magnifying side surface, which is convex. Its radius of curvature on its reducing side surface is ±∞, and its reducing side surface is flat. The refractive index of the fourth lens 21 is 1.7.

[0162] Lens 31 (fifth), 32 (sixth), and 33 (seventh) form the first cemented lens, also known as a three-cemented lens. The first cemented lens and lens 34 (eighth) form the third lens group 30. Lens 31 is a spherical lens with a radius of curvature of 305 mm on its magnifying side surface, which is convex. Its radius of curvature on its reducing side surface is -20 mm, and it is also convex. The Abbe number of lens 31 is 95. Lens 32 is a spherical lens with a radius of curvature of -20 mm on its magnifying side surface, which is concave. Its radius of curvature on its reducing side surface is 25 mm, and it is also concave. The refractive index of lens 32 is 1.74. Lens 33, the seventh lens, is a spherical lens with a radius of curvature of 25 mm on its magnifying side surface, which is convex. Its radius of curvature on its reducing side surface is -45 mm, and it is also convex. Lens 34, the eighth lens, is a spherical lens with a radius of curvature of 130 mm on its magnifying side surface, which is convex. Its radius of curvature on its reducing side surface is -50 mm, and it is also convex. The refractive index of lens 34 is 1.8.

[0163] The ninth lens 41 forms the fourth lens group 20. The ninth lens 41 is a spherical lens with a radius of curvature of 45 mm on its magnifying side surface and a convex surface shape. Its radius of curvature of -300 mm on its reducing side surface and a convex surface shape. The refractive index of the ninth lens 41 is 2.0.

[0164] It should be noted that the magnifying side surface of a lens is the side of the lens facing the projection side (i.e., the projected image). The reducing side surface of a lens is the side of the lens facing the image source (i.e., the DMD). When the radius of curvature of the magnifying side surface of a lens is positive, the magnifying side surface is convex, and vice versa; when the radius of curvature of the magnifying side surface is ±∞, the magnifying side surface is flat. When the radius of curvature of the reducing side surface of a lens is negative, the reducing side surface is convex, and vice versa; when the radius of curvature of the reducing side surface is ±∞, the reducing side surface is flat.

[0165] Specifically, the specific optical data of each lens in Example 1 are shown in Table 1 below.

[0166] Table 1 shows the specific optical data for each lens in Example 1.

[0167] In Example 1, as can be seen from Table 1 above, the optical power (also known as diopter) of the fifth lens 31 is positive, the optical power of the sixth lens 32 is negative, the optical power of the seventh lens 33 is positive, the optical power of the eighth lens 34 is positive, and the optical power of the ninth lens 41 is positive.

[0168] It is understandable that a biconvex lens (i.e., a lens with convex surfaces on both sides) has a positive focal length, meaning it has positive optical power. A biconcave lens (i.e., a lens with concave surfaces on both sides) has a negative focal length, meaning it has negative optical power.

[0169] As can be seen from Table 1 above, the first lens 11 is an aspherical lens. The first lens 11 has negative optical power. The second lens 12 also has negative optical power. The combination of the first lens 11 and the second lens 12 effectively expands the field of view and corrects distortion. The first lens 11 is a meniscus or M-shaped lens, which is beneficial for improving the field of view of the projection lens. The third lens 13 has a refractive index of 1.9. It can correct distortion and spherical aberration, as well as off-axis aberrations such as coma, field curvature, and astigmatism, ensuring a relatively gentle angle of incidence between the light and the lens surface, making it easy to process and manufacture.

[0170] In the second lens group 20, the fourth lens 21 has positive optical power, which has the function of collecting light and making the light transition of the entire optical path smoother, better correcting spherical aberration and astigmatism. In addition, the second lens group 20 can effectively control the front aperture, which is beneficial to improving the overall size and aperture of the lens.

[0171] In the third lens group 30, a combination of a cemented triplicate lens and a single lens is used, which effectively reduces the focal length of the third lens group 30, thus avoiding excessive zoom travel and reducing manufacturing difficulty. Furthermore, the use of a cemented triplicate lens, with the sixth lens in the cemented triplicate lens being a lens with low dispersion, can correct chromatic aberration and spherical aberration, improving brightness. Additionally, using a cemented triplicate lens can effectively shorten the length of the projection lens and reduce its size.

[0172] The fourth lens group can move along the optical axis, enabling more effective improvement in resolution at different sizes. Using lenses with a higher refractive index in the fourth lens group allows for correction of the telecentric angle, more effective control of the aperture, and thus a reduction in the size of the projection lens. Furthermore, using lenses with a higher refractive index in the fourth lens group also helps improve the edge performance of the lens and reduces the cost of the projection lens.

[0173] In Example 1, the projection lens satisfies the following conditions: -2.5 < F1 / Fs < -2.3; 2.6 < F2 / Fs < 3.3; 6.0 < F3 / Fs < 7.6; 2.5 < F4 / Fs < 3.1.

[0174] Wherein, F1 is the effective focal length of the first lens group 10; F2 is the effective focal length of the second lens group 20; F3 is the effective focal length of the third lens group 30; F4 is the effective focal length of the fourth lens group 40; and Fs is the wide-angle focal length of the projection lens.

[0175] For example, F1 / Fs can be -2.4, F2 / Fs can be 2.9, F3 / Fs can be 6.8, and F4 / Fs can be 2.8.

[0176] In this embodiment, the first lens group has a negative focal length, the second lens group has a positive focal length, the third lens group has a positive focal length, and the fourth lens group can also have a positive focal length. This enables three-element or two-element zoom, effectively reducing the number of structural groups and lowering the complexity of the projection lens. Furthermore, the use of front-group zoom in the projection lens reduces design difficulty and cost. Additionally, the negative focal length of the first lens group allows for control of the aperture and the wide-angle of the lens.

[0177] In Example 1, 10 < Fs / ZR < 12.7. Where ZR is the zoom ratio of the projection lens; Fs is the wide-angle focal length of the projection lens.

[0178] For example, Fs / ZR can be 11.3.

[0179] In this embodiment, without changing the zoom ratio, as the focal length decreases, the field of view and the projected size of the lens increase significantly; conversely, as the focal length increases, the field of view and the projected size decrease significantly. Therefore, the wide-angle focal length and zoom ratio of the projection lens in this embodiment satisfy the above conditions, enabling a larger magnification at the wide-angle end and improving the imaging performance at the wide-angle end.

[0180] In Example 1, the projection lens satisfies the following conditions: 0≤X2 / TTL≤0.1; 0.15≤BF / TTL.

[0181] Where X2 is the distance the second lens group 20 moves along the optical axis; BF is the back focal length of the projection lens; and TTL is the total optical length of the wide-angle end of the projection lens.

[0182] For example, X2 / TTL can be 0; BF / TTL can be 0.16. For example, X2 / TTL can be 0.08; BF / TTL can be 0.3. For example, X2 / TTL can be 0.1; BF / TTL can be 0.15.

[0183] In this embodiment, despite the limited overall optical length of the projection lens, a relatively long back focal length is achieved, which presents a significant design challenge but also results in superior imaging performance. Furthermore, while the overall optical length of the projection lens is limited, the movable distance of the front lens group (such as the second lens group) is relatively long, leading to a large magnification ratio for the projection lens, which, while challenging to design, also contributes to excellent imaging performance.

[0184] In Example 1, the projection lens satisfies the following condition: 1.9 ≤ F NO ≤3.0; 12≤Φ1 / F NO ≤16; 0.5≤Φ2 / BF≤1.7.

[0185] Among them, F NO Φ1 is the aperture number of the projection lens, which is the ratio of the effective focal length of the projection lens to the aperture diameter; Φ2 is the back focal length of the projection lens; Φ1 is the first aperture of the projection lens; Φ2 is the second aperture of the projection lens.

[0186] For example, F NO 2.2 can be taken; Φ1 / F NO Φ2 / BF can be taken as 14.4; Φ2 / BF can be taken as 0.5.

[0187] For example, F NO 2.5 can be taken; Φ1 / F NO Φ2 / BF can be taken as 13; Φ2 / BF can be taken as 1.2.

[0188] For example, F NO 3.0 can be taken; Φ1 / F NO Φ2 / BF can be taken as 12; Φ2 / BF can be taken as 1.7.

[0189] For example, F NO 3.0 can be taken; Φ1 / F NO Φ2 / BF can be taken as 16; Φ2 / BF can be taken as 1.5.

[0190] The projection lens provided in this embodiment has a large aperture number, enabling it to receive more light. In this embodiment, the ratio of the first aperture to the aperture number and the ratio of the second aperture to the back focal length satisfy the above conditions, ensuring that the projection lens can collect more light while maintaining a small size, resulting in a significant increase in brightness.

[0191] In Example 1, the projection lens satisfies the following condition: 1.0 ≤ STL / FL ≤ 1.6. Wherein, STL is the distance from the aperture stop to the specified lens; FL is the back focal length of the projection lens.

[0192] For example, STL / FL can be 1.0. For example, STL / FL can be 1.3. For example, STL / FL can be 1.6.

[0193] In the projection lens provided in this embodiment, the aperture stop is close to the rear lens group, which is difficult to design, but can reduce the total optical length of the projection lens and reduce the size of the lens.

[0194] In Example 1, the effective focal length F of the projection lens and the image plane height H of the projection lens are... image Satisfies: 1.4≤F / H image ≤2.4.

[0195] In this embodiment, the greater the image plane height, the shorter the focal length of the projection lens. Based on this, the effective focal length of the projection lens and the image plane height in the projection lens provided in this embodiment meet the corresponding conditions, which can achieve a larger focal length with fewer lenses. The design is difficult, but it can help reduce the size of the projection lens.

[0196] Example 2

[0197] As shown in Figure 5, the projection lens, from the projection side to the image source 90 along the same optical axis, includes: a first lens 11, a second lens 12, a third lens 13, a fourth lens 21, an aperture 50, a fifth lens 31, a sixth lens 32, an eighth lens 34, a ninth lens 41, a galvanometer (which can be represented as T) 60, a prism (which can be represented as P) 70, a light transmission protection device (which can be represented as CG) 80, and an image source 90.

[0198] The first lens 11, the second lens 12, and the third lens 13 constitute the first lens group 10. The first lens 11 has negative optical power; it is an aspherical lens with a radius of curvature of 100 mm on its magnifying side surface, which is convex, and a radius of curvature of 10 mm on its reducing side surface, which is concave. The second lens 12 has negative optical power; it is a spherical lens with a radius of curvature of -22 mm on its magnifying side surface, which is concave, and a radius of curvature of 40 mm on its reducing side surface, which is concave. The third lens 13 has positive optical power; it is a spherical lens with a radius of curvature of 117 mm on its magnifying side surface, which is convex, and a radius of curvature of -50 mm on its reducing side surface, which is convex. The refractive index of the third lens 13 is 1.9.

[0199] The fourth lens 21 forms part of the second lens group 20. The fourth lens 21 has positive optical power. The fourth lens 21 is a spherical lens with a radius of curvature of 28 mm on its magnifying side surface and a convex surface shape. Its radius of curvature of 1100 mm on its reducing side surface and a concave surface shape.

[0200] The fifth lens 31 and the sixth lens 32 form the second cemented lens, i.e., the cemented doublet. This cemented doublet and the eighth lens 34 form the third lens group 30. The fifth lens 31 is a spherical lens with a radius of curvature of 44 mm on its magnifying side surface, which is convex. Its radius of curvature of -10 mm on its reducing side surface is also convex. The Abbe number of the fifth lens 31 is 80. The sixth lens 32 is a spherical lens with a radius of curvature of -10 mm on its magnifying side surface, which is concave. Its radius of curvature of 40 mm on its reducing side surface is also concave. The refractive index of the sixth lens 32 is 1.74. The eighth lens 34 is an aspherical lens with a radius of curvature of 50 mm on its magnifying side surface, which is convex. Its radius of curvature of -29 mm on its reducing side surface is also convex. The refractive index of the eighth lens 34 is 1.8.

[0201] The ninth lens 41 forms the fourth lens group 20. The ninth lens 41 is a spherical lens with a radius of curvature of 25 mm on its magnifying side surface, which is convex. Its radius of curvature of the reducing side surface is 500 mm, and its reducing side surface is concave. The refractive index of the ninth lens 41 is 2.0.

[0202] Specifically, the specific optical data of each lens in Example 2 are shown in Table 2 below.

[0203] Table 2 shows the specific optical data for each lens in Example 2.

[0204] In Example 2, as shown in Table 2 above, the optical power of the fifth lens 31 is positive, the optical power of the sixth lens 32 is negative, the optical power of the eighth lens 34 is positive, and the optical power of the ninth lens 41 is positive.

[0205] It is understandable that a biconvex lens (i.e., a lens with convex surfaces on both sides) has a positive focal length, meaning it has positive optical power. A biconcave lens (i.e., a lens with concave surfaces on both sides) has a negative focal length, meaning it has negative optical power.

[0206] As can be seen from Table 2 above, the first lens 11 is an aspherical lens. The first lens 11 has negative optical power. The second lens 12 also has negative optical power. In this way, the first lens 11 and the second lens 12 work together to correct distortion. The first lens 11 is a meniscus or M-shaped lens, which is beneficial for improving the field of view of the projection lens. Furthermore, the third lens 13 has a refractive index of 1.9, which can correct distortion and spherical aberration, as well as off-axis aberrations such as coma, field curvature, and astigmatism. This ensures a relatively gentle angle of incidence between the light and the lens surface, making it easy to process and manufacture, and it can correct advanced aberrations.

[0207] In the second lens group 20, the fourth lens 21 has positive optical power, which has the function of collecting light and making the light transition of the entire optical path smoother, better correcting spherical aberration and astigmatism. In addition, the second lens group 20 can effectively control the front aperture, which is beneficial to improving the overall size and aperture of the lens.

[0208] In the third lens group 30, a doublet lens is used, and the fifth lens in this doublet is a lens with low dispersion, which can correct chromatic aberration and spherical aberration and improve brightness. In addition, the third lens group uses an aspherical lens (i.e., the eighth lens), which can correct the telecentric angle and increase the zoom ratio of the projection lens.

[0209] The fourth lens group can move along the optical axis, enabling more effective improvement in resolution at different sizes. Using lenses with a higher refractive index in the fourth lens group allows for correction of the telecentric angle, more effective control of the aperture, and thus a reduction in the size of the projection lens. Furthermore, using lenses with a higher refractive index in the fourth lens group also helps improve the edge performance of the lens and reduces the cost of the projection lens.

[0210] In summary, the projection lens provided in Example 2 has fewer lenses, which can improve the lens transmittance and enhance the brightness of the projection lens.

[0211] In Example 2, the projection lens satisfies the following conditions: -2.8 < F1 / Fs < -2.2; 2.9 < F2 / Fs < 3.8; 6.6 < F3 / Fs < 8.4; 2.3 < F4 / Fs < 2.9.

[0212] Wherein, F1 is the effective focal length of the first lens group 10; F2 is the effective focal length of the second lens group 20; F3 is the effective focal length of the third lens group 30; F4 is the effective focal length of the fourth lens group 40; and Fs is the wide-angle focal length of the projection lens.

[0213] For example, F1 / Fs can be -2.6, F2 / Fs can be 3.3, F3 / Fs can be 7.2, and F4 / Fs can be 2.4.

[0214] In this embodiment, the first lens group has a negative focal length, the second lens group has a positive focal length, the third lens group has a positive focal length, and the fourth lens group may also have a positive focal length. This enables three-element or two-element zoom, effectively reducing the number of structural groups and lowering the complexity of the projection lens. Furthermore, the use of front-group zoom reduces design difficulty and cost. Additionally, the negative focal length of the first lens group allows for control of the aperture and the lens's field of view, enabling diffused light at the wide-angle end of the projection lens.

[0215] In Example 2, 6.3 < Fs / ZR < 13. Where ZR is the zoom ratio of the projection lens; Fs is the wide-angle focal length of the projection lens.

[0216] For example, Fs / ZR can be 9.7.

[0217] In this embodiment, aspherical lenses are used in the rear group (i.e., the third lens group). This improves the zoom ratio when the total length of the projection lens is limited, thus mitigating the limitations imposed by the shorter total length. This, in turn, helps to reduce the size of the projection lens.

[0218] In Example 2, the projection lens satisfies the following conditions: 0.1≤X2 / TTL≤0.26; 0.13≤BF / TTL.

[0219] Where X2 is the distance the second lens group 20 moves along the optical axis; BF is the back focal length of the projection lens; and TTL is the total optical length of the wide-angle end of the projection lens.

[0220] For example, X2 / TTL can be 0.1; BF / TTL can be 0.2. For example, X2 / TTL can be 0.18; BF / TTL can be 0.26. For example, X2 / TTL can be 0.22; BF / TTL can be 0.13.

[0221] In this embodiment, despite the limited overall optical length of the projection lens, a relatively long back focal length is achieved, which presents a significant design challenge but also results in superior imaging performance. Furthermore, while the overall optical length of the projection lens is limited, the movable distance of the front lens group (such as the second lens group) is relatively long, leading to a large magnification ratio for the projection lens, which, while challenging to design, also contributes to excellent imaging performance.

[0222] In Example 2, the projection lens satisfies the following condition: 1.5 ≤ F NO ≤3.0; 10.2≤Φ1 / F NO ≤20.5; 0.7≤Φ2 / BF≤1.7.

[0223] Among them, F NOΦ1 is the aperture number of the projection lens, which is the ratio of the effective focal length of the projection lens to the aperture diameter; Φ2 is the back focal length of the projection lens; Φ1 is the first aperture of the projection lens; Φ2 is the second aperture of the projection lens.

[0224] For example, F NO 1.5 can be taken; Φ1 / F NO Φ2 / BF can be taken as 13; Φ2 / BF can be taken as 0.8.

[0225] For example, F NO 2.5 can be taken; Φ1 / F NO Φ2 / BF can be taken as 15; Φ2 / BF can be taken as 0.7.

[0226] For example, F NO 3.0 can be taken; Φ1 / F NO Φ2 / BF can be taken as 18; Φ2 / BF can be taken as 1.7.

[0227] For example, F NO 3.0 can be taken; Φ1 / F NO 20.5 can be taken; Φ2 / BF can be taken as 1.2.

[0228] The projection lens provided in this embodiment has a large aperture number, enabling it to receive more light. In this embodiment, the ratio of the first aperture to the aperture number and the ratio of the second aperture to the back focal length satisfy the above conditions, ensuring that the projection lens can collect more light while maintaining a small size, resulting in a significant increase in brightness.

[0229] In Example 2, the projection lens satisfies the following condition: 1.1 ≤ STL / FL ≤ 1.4. Wherein, STL is the distance from the aperture stop to the specified lens; FL is the back focal length of the projection lens.

[0230] For example, STL / FL can be 1.1. For example, STL / FL can be 1.2. For example, STL / FL can be 1.4.

[0231] In the projection lens provided in this embodiment, the aperture stop is close to the rear lens group, which is difficult to design, but can reduce the total optical length of the projection lens and reduce the size of the lens.

[0232] In Example 2, the effective focal length F of the projection lens and the image plane height H of the projection lens are... image Satisfies: 1.4≤F / H image ≤2.4.

[0233] In this embodiment, the greater the image plane height, the shorter the focal length of the projection lens. Based on this, the effective focal length of the projection lens and the image plane height in the projection lens provided in this embodiment meet the corresponding conditions, which can achieve a larger focal length with fewer lenses. The design is difficult, but it can help reduce the size of the projection lens.

[0234] Example 3

[0235] As shown in Figure 6, the projection lens, from the projection side to the image source 90 along the same optical axis, includes: a first lens 11, a second lens 12, a third lens 13, a fourth lens 21, an aperture 50, a fifth lens 31, a sixth lens 32, a seventh lens 33, an eighth lens 34, a tenth lens 35, a ninth lens 41, a galvanometer (which can be represented as T) 60, a prism (which can be represented as P) 70, a light transmission protection device (which can be represented as CG) 80, and an image source 90.

[0236] The first lens 11, the second lens 12, and the third lens 13 constitute the first lens group 10. The first lens 11 has negative optical power; it is an aspherical lens with a radius of curvature of 36 mm on its magnifying side surface, which is convex, and a radius of curvature of 11 mm on its reducing side surface, which is concave. The second lens 12 has negative optical power; it is a spherical lens with a radius of curvature of -28 mm on its magnifying side surface, which is concave, and a radius of curvature of 37 mm on its reducing side surface, which is concave. The third lens 13 has positive optical power; it is a spherical lens with a radius of curvature of 130 mm on its magnifying side surface, which is convex, and a radius of curvature of -55 mm on its reducing side surface, which is convex. The refractive index of the third lens 13 is 1.88.

[0237] The fourth lens 21 forms part of the second lens group 20. The fourth lens 21 has positive optical power. The fourth lens 21 is a spherical lens with a radius of curvature of 34 mm on its magnifying side surface, which is convex. Its radius of curvature of -420 mm on its reducing side surface is also convex. The refractive index of the fourth lens 21 is 1.91.

[0238] Lens 31 (fifth), 32 (sixth), and 33 (seventh) form the first cemented lens, i.e., a cemented triplet lens. Lens 34 (eighth) and 35 (tenth) form the second cemented lens, i.e., a cemented doublet lens. These first and second cemented lenses together form the third lens group 30. Lens 31 is a spherical lens with a radius of curvature of 50 mm on its magnifying side surface, which is convex. Its radius of curvature on its reducing side surface is -15 mm, and it is also convex. Lens 32 is a spherical lens with a radius of curvature of -15 mm on its magnifying side surface, which is concave. Its radius of curvature on its reducing side surface is 16 mm, and it is also concave. The refractive index of lens 32 is 1.84. Lens 33 (Seventh Lens) is a spherical lens with a radius of curvature of 16 mm on its magnifying side surface, which is convex. Its radius of curvature on its reducing side surface is -25 mm, and it is also convex. The Abbe number of lens 33 is 80. Lens 34 (Eighth Lens) is a spherical lens with a radius of curvature of -15 mm on its magnifying side surface, which is concave. Its radius of curvature on its reducing side surface is -300 mm, and it is also convex. The refractive index of lens 34 is 1.72. Lens 35 (Tenth Lens) is a spherical lens with a radius of curvature of -300 mm on its magnifying side surface, which is concave. Its radius of curvature on its reducing side surface is -18 mm, and it is also convex.

[0239] The ninth lens 41 forms the fourth lens group 20. The ninth lens 41 is a spherical lens with a radius of curvature of 50 mm on its magnifying side surface and a convex surface shape. Its radius of curvature of -200 mm on its reducing side surface and a convex surface shape. The refractive index of the ninth lens 41 is 1.92.

[0240] Specifically, the specific optical data of each lens in Example 3 are shown in Table 3 below.

[0241] Table 3 shows the specific optical data for each lens in Example 3.

[0242] In Example 3, from Table 3 and Formula (2) above, it can be seen that the optical power of the fifth lens 31 is positive, the optical power of the sixth lens 32 is negative, the optical power of the seventh lens 33 is positive, the optical power of the eighth lens 34 is positive, the optical power of the tenth lens 35 is positive, and the optical power of the ninth lens 41 is positive.

[0243] Formula 2 is as follows: D=(N-1)(1 / R1+1 / R2) (2)

[0244] Where D represents the optical power (i.e., diopter) of the lens; N is the refractive index of the lens; R1 is the radius of curvature of the magnifying side surface of the lens; and R2 is the radius of curvature of the reducing side surface of the lens.

[0245] It is understandable that a biconvex lens (i.e., both sides of the lens are convex) has a positive focal length, meaning it has positive optical power. A biconcave lens (i.e., both sides of the lens are concave) has a negative focal length, meaning it has negative optical power. Furthermore, for a meniscus lens (one side of the lens is convex and the other side is concave), the optical power can be calculated based on the lens's refractive index and the radii of curvature on both sides, as shown in Formula 2 above.

[0246] As can be seen from Table 3 above, the first lens 11 is an aspherical lens. The first lens 11 has negative optical power. The second lens 12 also has negative optical power. In this way, the first lens 11 and the second lens 12 work together to correct distortion. The first lens 11 is a meniscus or M-shaped lens, which is beneficial for improving the field of view of the projection lens. Furthermore, the third lens 13 has a refractive index of 1.88, which can correct distortion and spherical aberration, as well as off-axis aberrations such as coma, field curvature, and astigmatism, ensuring a relatively gentle angle of incidence between the light and the lens surface, making it easy to process and manufacture.

[0247] In the second lens group 20, the fourth lens 21 has positive optical power, which has the function of collecting light and making the light transition of the entire optical path smoother, better correcting spherical aberration and astigmatism. In addition, the second lens group 20 can effectively control the front aperture, which is beneficial to improving the overall size and aperture of the lens.

[0248] In the third lens group 30, a combination of a cemented triplicate lens and a cemented doublicate lens is used, and the seventh lens in the cemented triplicate lens is a lens with low dispersion. This can correct chromatic aberration and spherical aberration, as well as higher aberrations, and improve the transmittance and brightness of the projection lens. In addition, the combination of a cemented triplicate lens and a cemented doublicate lens can effectively shorten the length of the projection lens, reduce the lens size, and achieve miniaturization of the projection lens.

[0249] The fourth lens group can move along the optical axis, enabling more effective improvement in resolution at different sizes. Using lenses with a higher refractive index in the fourth lens group allows for correction of the telecentric angle, more effective control of the aperture, and thus a reduction in the size of the projection lens. Furthermore, using lenses with a higher refractive index in the fourth lens group also helps improve the edge performance of the lens and reduces the cost of the projection lens.

[0250] In Example 3, the projection lens satisfies the following conditions: -2.7 < F1 / Fs < -2.0; 2.2 < F2 / Fs < 3.8; -104 < F3 / Fs < -83; 2.0 < F4 / Fs < 2.5.

[0251] Wherein, F1 is the effective focal length of the first lens group 10; F2 is the effective focal length of the second lens group 20; F3 is the effective focal length of the third lens group 30; F4 is the effective focal length of the fourth lens group 40; and Fs is the wide-angle focal length of the projection lens.

[0252] For example, F1 / Fs can be -2.2, F2 / Fs can be 3.6, F3 / Fs can be -100, and F4 / Fs can be 2.2.

[0253] In this embodiment, the first lens group has a negative focal length, the second lens group has a positive focal length, the third lens group has a positive focal length, and the fourth lens group can also have a positive focal length. This enables three-element or two-element zoom, effectively reducing the number of structural groups and lowering the complexity of the projection lens. Furthermore, the use of front-group zoom reduces design difficulty and cost. Additionally, the negative focal length of the first lens group allows for control of the aperture and the lens's field of view, enabling diffused light at the wide-angle end of the projection lens.

[0254] In Example 3, 6.0 < Fs / ZR < 16. Where ZR is the zoom ratio of the projection lens; Fs is the wide-angle focal length of the projection lens.

[0255] For example, Fs / ZR can be 12.

[0256] In this embodiment, the focal length and zoom ratio of the projection lens at the wide-angle end can meet the above conditions, thus achieving a larger magnification at the wide-angle end and improving the imaging performance at the wide-angle end.

[0257] In Example 3, the projection lens satisfies the following conditions: 0.1≤X2 / TTL≤0.3; 0.11≤BF / TTL.

[0258] Where X2 is the distance the second lens group 20 moves along the optical axis; BF is the back focal length of the projection lens; and TTL is the total optical length of the wide-angle end of the projection lens.

[0259] For example, X2 / TTL can be 0.1; BF / TTL can be 0.2. For example, X2 / TTL can be 0.18; BF / TTL can be 0.3. For example, X2 / TTL can be 0.3; BF / TTL can be 0.11.

[0260] In this embodiment, despite the limited overall optical length of the projection lens, a relatively long back focal length is achieved, which presents a significant design challenge but also results in superior imaging performance. Furthermore, while the overall optical length of the projection lens is limited, the movable distance of the front lens group (such as the second lens group) is relatively long, leading to a large magnification ratio for the projection lens, which, while challenging to design, also contributes to excellent imaging performance.

[0261] In Example 3, the projection lens satisfies the following condition: 1.7 ≤ F NO ≤3.0; 9.5≤Φ1 / F NO ≤25; 0.7≤Φ2 / BF≤1.7.

[0262] Among them, F NO Φ1 is the aperture number of the projection lens, which is the ratio of the effective focal length of the projection lens to the aperture diameter; Φ2 is the back focal length of the projection lens; Φ1 is the first aperture of the projection lens; Φ2 is the second aperture of the projection lens.

[0263] For example, F NO 1.7 can be taken; Φ1 / F NO Φ2 / BF can be taken as 13; Φ2 / BF can be taken as 0.8.

[0264] For example, F NO 2.5 can be taken; Φ1 / F NO 9.5 can be taken; Φ2 / BF can be taken as 0.7.

[0265] For example, F NO 3.0 can be taken; Φ1 / F NO Φ2 / BF can be taken as 18; Φ2 / BF can be taken as 1.7.

[0266] For example, F NO 3.0 can be taken; Φ1 / F NO 25 can be taken; Φ2 / BF can be taken as 1.2.

[0267] The projection lens provided in this embodiment has a large aperture number, enabling it to receive more light. In this embodiment, the ratio of the first aperture to the aperture number and the ratio of the second aperture to the back focal length satisfy the above conditions, ensuring that the projection lens can collect more light while maintaining a small size, resulting in a significant increase in brightness.

[0268] In Example 3, the projection lens satisfies the following condition: 1.0 ≤ STL / FL ≤ 1.6. Wherein, STL is the distance from the aperture stop to the specified lens; FL is the back focal length of the projection lens.

[0269] For example, STL / FL can be 1.0. For example, STL / FL can be 1.5. For example, STL / FL can be 1.6.

[0270] In the projection lens provided in this embodiment, the aperture stop is close to the rear lens group, which is difficult to design, but can reduce the total optical length of the projection lens and reduce the size of the lens.

[0271] In Example 3, the effective focal length F of the projection lens and the image plane height H of the projection lens are... image Satisfies: 1.4≤F / H image ≤2.4.

[0272] In this embodiment, the greater the image plane height, the shorter the focal length of the projection lens. Based on this, the effective focal length of the projection lens and the image plane height in the projection lens provided in this embodiment meet the corresponding conditions, which can achieve a larger focal length with fewer lenses. The design is difficult, but it can help reduce the size of the projection lens.

[0273] This application also provides a projection device, which includes a housing and a projection lens as described in the above embodiment, the projection lens being disposed in the housing.

[0274] The specific structure of the projection lens can be found in the various embodiments described above.

[0275] Since the projection device of this application uses the projection lens of all the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be described in detail here.

[0276] The above-described 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, and should all be included within the protection scope of this application.

Claims

1. A projection lens characterized in that, The projection lens comprises, from the projection side to the image source along the same optical axis, a first lens group (10), a second lens group (20), a third lens group (30), and a fourth lens group (40). At least two of the first lens group (10), the second lens group (20), and the third lens group (30) are zoom groups, which can move along the optical axis to change the focal length of the projection lens. The fourth lens group (40) can move along the optical axis, or the fourth lens group (40) is a fixed lens group. Among them, when the zoom group with the longest moving distance moves towards the projection side and moves to the first position, the projection lens switches to telephoto mode. When the zoom group that has moved the longest distance moves toward the image source, and the projection lens switches to wide-angle mode when it reaches the second position.

2. The projection lens according to claim 1, characterized in that The first lens group (10), the second lens group (20), and the third lens group (30) are all zoom groups; wherein, The fourth lens group (40) is a fixed lens group, and the first lens group (10) can move along the optical axis to focus; or, the fourth lens group (40) can move along the optical axis to focus.

3. The projection lens of claim 1, wherein The second lens group (20) and the third lens group (30) constitute the zoom group; Wherein, the fourth lens group (40) is a fixed lens group, and the first lens group (10) can move along the optical axis to perform focusing; or, the first lens group (10) is a fixed lens group, and the fourth lens group (40) can move along the optical axis to perform focusing.

4. The projection lens of claim 1, wherein The first lens group (10) includes a first lens (11), a second lens (12), and a third lens (13); wherein, The first lens (11) has negative optical power; The second lens (12) has negative optical power; The third lens (13) has positive optical power; The second lens group (20) has positive optical power; The third lens group (30) includes at least one set of cemented lenses, and the cemented lenses have positive or negative optical power.

5. The projection lens according to claim 4, characterized in that The first lens group (10) includes at least one aspherical lens; And / or, at least one lens in the first lens group (10) has a refractive index greater than or equal to 1.7; And / or, the first lens (11) is an aspherical lens; And / or, the refractive index of the third lens (13) is greater than or equal to 1.7; And / or, at least one lens in the second lens group (20) has a refractive index greater than or equal to 1.7; And / or, at least one lens in the third lens group (30) has a refractive index greater than or equal to 1.7; And / or, at least one lens in the third lens group (30) has an Abbe number greater than or equal to 70; And / or, at least one lens in the third lens group (30) is an aspherical lens; And / or, the cemented lens is made of two or three lenses cemented together.

6. The projection lens of claim 4, wherein, The magnifying side surface of the first lens is convex, and the reducing side surface of the first lens is concave. The magnifying side surface of the second lens is concave, and the reducing side surface of the second lens is concave. The magnifying side surface of the third lens is convex, and the reducing side surface of the third lens is also convex.

7. The projection lens of claim 4, wherein The second lens group (20) includes a fourth lens (21) having a refractive index greater than or equal to 1.7; The third lens group (30) includes a first cemented lens and an eighth lens (34); wherein the first cemented lens is formed by cementing the fifth lens (31) and the sixth lens (32) together, or by cementing the fifth lens (31), the sixth lens (32) and the seventh lens (33) together; Wherein, the third lens group satisfies at least one of the following: The Abbe number of at least one lens in the first cemented lens is greater than or equal to 70; The refractive index of at least one lens in the first cemented lens is greater than or equal to 1.7; The refractive index of the eighth lens (34) is greater than or equal to 1.

7.

8. The projection lens of claim 7, wherein, The magnifying side surface of the fourth lens is convex, and the reducing side surface of the fourth lens is either flat or concave. The magnifying side surface of the fifth lens is convex, and the reducing side surface of the fifth lens is convex. The magnifying side surface of the sixth lens is concave, and the reducing side surface of the sixth lens is also concave. The magnifying side surface of the seventh lens is convex, and the reducing side surface of the seventh lens is convex. The magnifying side surface of the eighth lens is convex, and the reducing side surface of the eighth lens is also convex.

9. The projection lens of claim 1, wherein, The fourth lens group (40) includes a ninth lens (41), the refractive index of the ninth lens (41) is greater than or equal to 1.9, the magnifying side surface of the ninth lens is convex, and the reducing side surface of the ninth lens is either convex or concave.

10. The projection lens according to any one of claims 1-3, wherein, The wide-angle focal length of the projection lens is Fs, which is the focal length of the projection lens in the wide-angle mode; the effective focal length of the first lens group is F1, the effective focal length of the second lens group is F2, the effective focal length of the third lens group is F3, and the effective focal length of the fourth lens group is F4; wherein... The effective focal length F1 of the first lens group and the wide-angle focal length Fs satisfy: -5.6 < F1 / Fs < -1.0; The effective focal length F2 of the second lens group and the wide-angle focal length Fs satisfy: 0.6 < F2 / Fs < 6.3; The effective focal length F3 of the third lens group and the wide-angle focal length Fs satisfy: 4.0 < F3 / Fs < 9.6, or -120 < F3 / Fs < -70; The effective focal length F4 of the fourth lens group and the wide-angle focal length Fs satisfy: 0.5 < F4 / Fs < 5.

1.

11. The projection lens according to any one of claims 1-3, wherein, The zoom ratio of the projection lens is ZR, which is the ratio of the focal length at the telephoto end to the focal length at the wide-angle end of the projection lens. The telephoto end focal length is the focal length of the projection lens in telephoto mode, and the wide-angle end focal length is the focal length of the projection lens in wide-angle mode. The zoom ratio ZR and the wide-angle focal length Fs satisfy: 6.0 < Fs / ZR < 16.

8.

12. The projection lens according to any one of claims 1-3, wherein, The distance the second lens group (20) moves along the optical axis is X2; the back focal length of the projection lens is BF; the back focal length is the distance between the reduced-size side surface of the designated lens and the image source on the optical axis; the designated lens is the lens in the projection lens closest to the image source; the reduced-size side surface of the designated lens is the surface facing the image source; the total optical length at the wide-angle end of the projection lens is TTL; the total optical length at the wide-angle end is the total optical length of the projection lens in the wide-angle mode; wherein... The distance X2 that the second lens group moves along the optical axis satisfies the following condition with respect to the total optical length TTL at the wide-angle end: 0 ≤ X2 / TTL ≤ 0.3; The back focal length BF of the projection lens and the total optical length TTL of the wide-angle end satisfy the condition: 0.1≤BF / TTL.

13. The projection lens according to any one of claims 1-3, wherein, The projection lens has an F-number of F NO , a back focal length BF, the back focal length being a distance on the optical axis between a reduction side surface of a specified lens and the image source, the specified lens being a lens closest to the image source in the projection lens, the reduction side surface of the specified lens being a surface toward the image source; a first aperture Φ1 of the projection lens, the first aperture being an aperture of a lens closest to the projection side in the projection lens; and a second aperture Φ2 of the projection lens, the second aperture being an aperture of the specified lens, wherein, The number of apertures F NO satisfies: 1.5 ≤ F NO ≤ 3.0; The first caliber Φ1 and the aperture number F NO Satisfy: 6.6≤Φ1 / F NO ≤40; The second aperture Φ2 and the back focal length BF of the projection lens satisfy the following condition: 0.5≤Φ2 / BF≤1.

7.

14. The projection lens according to any one of claims 1-3, wherein, The projection lens also includes an aperture stop, which is located between the second lens group (20) and the third lens group (30). When the third lens group (30) moves along the optical axis, the aperture stop moves with the third lens group (30). The distance between the aperture stop and the designated lens is STL, the designated lens is the lens in the projection lens that is closest to the image source, the rear focal length of the projection lens is FL, the rear focal length is the effective focal length of the rear lens group of the projection lens, and the rear lens group includes the third lens group (30) and the fourth lens group (40). Wherein, the STL and the rear focal length FL of the projection lens satisfy: -5.0≤STL / FL≤6.

0.

15. The projection lens according to any one of claims 1-3, wherein, The effective focal length of the projection lens is F, and the image height of the projection lens is H image wherein, An effective focal length F of the projection lens and an image height H of the projection lens satisfy: 1.4 ≤ F / H ≤ 2.

4. image An effective focal length F of the projection lens and an image height H of the projection lens satisfy: 1.4 ≤ F / H ≤ 2.

4. image An effective focal length F of the projection lens and an image height H of the projection lens satisfy: 1.4 16. A projection apparatus, characterized by, The projection device includes: case; And a projection lens as described in any one of claims 1-15, wherein the projection lens is disposed in the housing.

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