A large aperture zoom projection lens

Abstract

The application discloses a large-aperture zoom projection lens, and relates to the technical field of projection lenses, comprising a first lens group, a second lens group, a third lens group, a fourth lens group, a fifth lens group, a sixth lens group and a seventh lens group which are sequentially arranged along an optical axis from a magnifying side to a reducing side; the first lens group and the seventh lens group are fixed, and the lens groups satisfy the following conditional expressions: 4.5<=f1 / fw<=6.0, 6.0<=|f2| / fw<=7.3, 1.2<=|f3| / fw<=2.5, 0.9<=|f7| / fw<=1.8, f1 is the focal length of the first lens group, f2 is the focal length of the second lens group, f3 is the focal length of the third lens group, f7 is the focal length of the seventh lens group, and fw is the focal length of the lens at a wide-angle end. The large-aperture zoom projection lens can keep the projection picture clear without refocusing after zooming under specific parameters, and the zooming is more convenient.

Description

Technical Field

[0001] This invention relates to the field of projection lens technology, and in particular to a large aperture zoom projection lens. Background Technology

[0002] Projection lenses are used in projectors and other projection devices to magnify and project small images onto a screen or wall. At the same projection distance, different users have different magnification requirements, and zooming with a projection lens can change this magnification. However, with certain projection lenses, such as the one with publication number CN119224988A, zooming without changing the projection distance will result in a blurry image, requiring refocusing to restore clarity. Summary of the Invention

[0003] This invention aims to at least solve one of the technical problems existing in the prior art. To this end, this invention proposes a large-aperture zoom projection lens that, under specific specifications, maintains a clear projected image without the need for refocusing after zooming, and makes zooming more convenient.

[0004] According to an embodiment of the present invention, a large-aperture zoom projection lens includes a first lens group, a second lens group, a third lens group, a fourth lens group, a fifth lens group, a sixth lens group, and a seventh lens group arranged sequentially along the optical axis from the magnification side to the reduction side; the first lens group and the seventh lens group are both fixed, and the first lens group, the second lens group, the third lens group, and the seventh lens group also satisfy the following condition:

[0005] 4.5≤f1 / fw≤6.0,

[0006] 6.0≤|f2| / fw≤7.3,

[0007] 1.2≤|f3| / fw≤2.5,

[0008] 0.9≤|f7| / fw≤1.8,

[0009] Where f1 is the focal length of the first lens group, f2 is the focal length of the second lens group, f3 is the focal length of the third lens group, f7 is the focal length of the seventh lens group, and fw is the focal length of the lens at the wide-angle end.

[0010] The large-aperture zoom projection lens according to embodiments of the present invention has at least the following beneficial effects: the projection lens adopts the structure provided by the present invention and satisfies the conditions 4.5≤f1 / fw≤6.0, 6.0≤|f2| / fw≤7.3, 1.2≤|f3| / fw≤2.5, 0.9≤|f7| / fw≤1.8, which enables a clear projected image without refocusing after zooming without changing the projection distance; both the first lens group and the seventh lens group are fixed, and the total length of the lens does not change when the projection lens performs zooming operations, which is beneficial to the simplified design of the lens structure of the projection device and can obtain better dustproof and waterproof effects.

[0011] According to some embodiments of the present invention, the lens also satisfies the following condition:

[0012] 1.5≤BF / fw≤1.8

[0013] Where BF is the back focal equivalent air length of the lens, and fw is the focal length of the lens at the wide-angle end.

[0014] According to some embodiments of the present invention, the second lens group is a focusing group.

[0015] According to some embodiments of the present invention, during the focusing process from infinity to close distance on the magnifying side of the lens, the second lens group moves along the optical axis from the reducing side toward the magnifying side.

[0016] According to some embodiments of the present invention, the third lens group, the fourth lens group, the fifth lens group and the sixth lens group are all zoom groups, and the third lens group, the fourth lens group, the fifth lens group and the sixth lens group are all capable of moving independently of each other along the optical axis.

[0017] According to some embodiments of the present invention, during the zooming process of the lens from short to long effective focal length, the third lens group moves along the optical axis from the magnification side to the reduction side.

[0018] According to some embodiments of the present invention, the effective focal length of the lens is increased from short to long during the zoom process, including a first zoom segment and a second zoom segment. In the first zoom segment, the fourth lens group moves along the optical axis from the reduction side to the magnification side. In the second zoom segment, the fourth lens group moves along the optical axis from the magnification side to the reduction side.

[0019] According to some embodiments of the present invention, during the zooming process of the lens from short to long effective focal length, the fifth lens group moves along the optical axis from the shrinking side to the magnifying side.

[0020] According to some embodiments of the present invention, during the zooming process of the lens from short to long effective focal length, the sixth lens group moves along the optical axis from the shrinking side to the magnifying side.

[0021] According to some embodiments of the present invention, the aperture of the lens remains constant during zooming.

[0022] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0023] The present invention will be further described below with reference to the accompanying drawings and embodiments, wherein:

[0024] Figure 1 This is a schematic diagram of the large aperture zoom projection lens at the Wide end according to an embodiment of the present invention;

[0025] Figure 2 This is a schematic diagram of the large aperture zoom projection lens at the Middle end according to an embodiment of the present invention.

[0026] Figure 3 This is a schematic diagram of the structure of the large aperture zoom projection lens at the Tele end according to an embodiment of the present invention;

[0027] Figure 4 This is a light aberration diagram of the large aperture zoom projection lens at the Wide end in an embodiment of the present invention.

[0028] Figure 5 This is a diagram showing chromatic aberration, astigmatism, and distortion of a large-aperture zoom projection lens at the Wide end in an embodiment of the present invention.

[0029] Figure 6 This is a light aberration diagram of the large aperture zoom projection lens at the Middle end in an embodiment of the present invention.

[0030] Figure 7 The image shows the chromatic aberration, astigmatism, and distortion of the large-aperture zoom projection lens at the Middle end in an embodiment of the present invention.

[0031] Figure 8 This is a light aberration diagram of the large aperture zoom projection lens at the Tele end in an embodiment of the present invention.

[0032] Figure 9 This is a diagram showing the chromatic aberration, astigmatism, and distortion of the large-aperture zoom projection lens at the Tele end in an embodiment of the present invention.

[0033] Icon labels:

[0034] First lens group 100, second lens group 200, third lens group 300, fourth lens group 400, fifth lens group 500, sixth lens group 600, seventh lens group 700. Detailed Implementation

[0035] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0036] In the description of this invention, it should be understood that the orientation descriptions, such as up, down, etc., are based on the orientation or positional relationship shown in the drawings and are only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0037] In the description of this invention, "multiple" refers to two or more. The use of "first" and "second" is for distinguishing technical features only and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features or their sequential relationship.

[0038] In the description of this invention, unless otherwise explicitly defined, terms such as "set up," "install," and "connect" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this invention in conjunction with the specific content of the technical solution.

[0039] As described in the background section, taking a home projector as an example, after the home projector is fixedly installed, a screen is placed 3 meters in front of the projector, i.e., the projection distance is 3 meters. An 80-inch image is projected onto the screen, and after focusing, a clear image is obtained. While maintaining the projection distance of 3 meters, zooming the projection lens can scale the projected image size, for example, enlarging the projected image to 100 inches. However, with existing projection lenses, the image becomes blurry after zooming, requiring refocusing to obtain a clear image again. However, focusing the projection lens is relatively complex. Although existing technology can achieve automatic focusing, the effect is not satisfactory, ultimately requiring manual fine-tuning to obtain the best image clarity. If refocusing is required every time the projection lens is zoomed, it will negatively impact the user experience.

[0040] Reference Figure 1As shown, an embodiment of the large-aperture zoom projection lens of the present invention includes a first lens group 100, a second lens group 200, a third lens group 300, a fourth lens group 400, a fifth lens group 500, a sixth lens group 600, and a seventh lens group 700 arranged sequentially along the optical axis from the magnification side to the reduction side; the first lens group 100 and the seventh lens group 700 are both fixed, and the first lens group 100, the second lens group 200, the third lens group 300, and the seventh lens group 700 also satisfy the following conditional expression:

[0041] 4.5≤f1 / fw≤6.0,

[0042] 6.0≤|f2| / fw≤7.3,

[0043] 1.2≤|f3| / fw≤2.5,

[0044] 0.9≤|f7| / fw≤1.8,

[0045] Where f1 is the focal length of the first lens group 100, f2 is the focal length of the second lens group 200, f3 is the focal length of the third lens group 300, f7 is the focal length of the seventh lens group 700, and fw is the focal length of the lens at the wide-angle end.

[0046] The projection lens using the structure of this invention can achieve a clear image after zooming without refocusing, while maintaining the same projection distance. This significantly reduces the complexity of user operation and improves the user experience. It should be understood that, as a projection lens, the magnifying side refers to the side where the image is projected, i.e., the screen location, while the reducing side refers to the side where the projector outputs the image, i.e., the side where the prism group is located in the seventh lens group 700.

[0047] It is understandable that the first lens group 100 and the seventh lens group 700 are both fixed. The total length of the lens will not change during the zoom process. This means that the lens installation position of the projector does not need to be adjusted to adapt to the change in lens length. In other words, the structure of the projector can be simplified and better dustproof and waterproof performance can be achieved.

[0048] It should be understood that a lens group can consist of a single lens or multiple lenses, and this invention does not limit the number of lenses in a single lens group.

[0049] Preferably, the lens also satisfies the following condition:

[0050] 1.5≤BF / fw≤1.8

[0051] Where BF is the back focal equivalent air length of the lens, and fw is the focal length of the lens at the wide-angle end.

[0052] Preferably, the second lens group 200 is a focusing group. During the focusing process from infinity to close distance on the magnifying side of the lens, the second lens group 200 moves along the optical axis from the reducing side to the magnifying side. Here, "close distance" is relative to infinity. The emphasis is on the direction from infinity to close distance. It should be understood that regardless of how many values ​​are defined as close distance, the directional nature of the direction from infinity to close distance will not change.

[0053] It is important to understand that the second lens group 200, acting as a focusing group, can be used for focusing when the projection distance changes. During the initial projection or when the projection distance changes, the second lens group 200 needs to be used for focusing to obtain a clear projected image. Subsequent zoom operations while maintaining the same projection distance do not require readjusting the position of the second lens group 200, i.e., no further focusing is needed.

[0054] Preferably, the third lens group 300, the fourth lens group 400, the fifth lens group 500 and the sixth lens group 600 are all zoom groups, and the third lens group 300, the fourth lens group 400, the fifth lens group 500 and the sixth lens group 600 can all move independently along the optical axis.

[0055] Preferably, the zoom process of the lens from short to long effective focal length includes a first zoom segment and a second zoom segment. In the first zoom segment, the fourth lens group 400 moves along the optical axis from the reduction side to the magnification side. In the second zoom segment, the fourth lens group 400 moves along the optical axis from the magnification side to the reduction side. Throughout the entire zoom process of the lens from short to long effective focal length, the third lens group 300 moves along the optical axis from the magnification side to the reduction side; the fifth lens group 500 moves along the optical axis from the reduction side to the magnification side; and the sixth lens group 600 moves along the optical axis from the reduction side to the magnification side.

[0056] Preferably, the aperture of the lens remains constant during zooming. In some existing projection lenses, the aperture increases when the lens is at a short focal length (wide-angle end) and decreases when it is at a long focal length, resulting in excessive loss of light energy transmitted through the lens. If the lens aperture is kept constant during zooming, the loss of light energy can be reduced. The lens structure of this embodiment, through reasonable optical power lens and lens group design, maintains a constant ratio of lens focal length to entrance pupil diameter during zooming, thus achieving a constant aperture during zooming.

[0057] Example 1:

[0058] The lens has an effective focal length (EFL) of 15.1mm at the wide end and 45.3mm at the telephoto end. The aperture is f / 1.7. The field of view (2ω) is 31.9°. The lens also satisfies the following conditions:

[0059] f1 / fw=5.43, |f2| / fw=6.81, |f3| / fw=1.78, f7 / fw=1.30, BF / fw=1.95.

[0060] The remaining parameters of the projection lens in Example 1 are shown in Table 1, and the optical structure is as follows: Figures 1 to 3 As shown.

[0061] Table 1. Parameters of the optical lens in Example 1

[0062]

[0063]

[0064] The focusing interval data for the lens in Example 1 is shown in Table 2.

[0065] Table 2 Lens spacing data for Example 1

[0066] FAR Middle Near D0 1500 3000 7000 D1 0.5 1.91 4.52 D2 13.42 12.55 15.16

[0067] The zoom interval data of the lens in Example 1 during zooming is shown in Table 3.

[0068] Table 3. Zoom interval data of the lens in Example 1

[0069] Wide Middle Tele D2 12.55 16.65 16.87 D3 29.55 4.09 1.70 D4 4.13 10.88 0.5 D5 0.5 4.29 9.07 D6 0.5 11.32 19.08

[0070] The D0 to D6 in Tables 2 and 3 above are the same as the D0 to D6 in Table 1.

[0071] The light aberration at the wide end of the lens in Example 1 is as follows: Figure 4 As shown; chromatic aberration, image scatter curvature, and distortion are shown in the image. Figure 5 As shown. The light aberration of the lens at the Middle end in Example 1 is as follows. Figure 6 As shown; chromatic aberration, image scatter curvature, and distortion are shown in the image. Figure 7 As shown. The light aberrations of the lens at the Telephone end in Example 1 are as follows. Figure 8 As shown; chromatic aberration, image scatter curvature, and distortion are shown in the image. Figure 9 As shown.

[0072] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A large aperture zoom projection lens, characterized in that, include: The first lens group (100), the second lens group (200), the third lens group (300), the fourth lens group (400), the fifth lens group (500), the sixth lens group (600) and the seventh lens group (700) are arranged sequentially along the optical axis from the magnification side to the reduction side. The first lens group (100) has positive optical power, the second lens group (200) has negative optical power, the third lens group (300) has negative optical power, the fourth lens group (400) has positive optical power, the fifth lens group (500) has positive optical power, the sixth lens group (600) has positive optical power, and the seventh lens group (700) has positive optical power. The second lens group (200) is a focusing group, and the third lens group (300), the fourth lens group (400), the fifth lens group (500) and the sixth lens group (600) are all zoom groups, and the third lens group (300), the fourth lens group (400), the fifth lens group (500) and the sixth lens group (600) can all move independently along the optical axis; Both the first lens group (100) and the seventh lens group (700) are fixed. The first lens group (100), the second lens group (200), the third lens group (300), and the seventh lens group (700) also satisfy the following condition: 4.5≤f1 / fw≤6.0, 6.0≤|f2| / fw≤7.3, 1.2≤|f3| / fw≤2.5, 0.9≤|f7| / fw≤1.8, Wherein, f1 is the focal length of the first lens group (100), f2 is the focal length of the second lens group (200), f3 is the focal length of the third lens group (300), f7 is the focal length of the seventh lens group (700), and fw is the focal length of the lens at the wide-angle end.

2. The large aperture zoom projection lens according to claim 1, characterized in that, The lens also satisfies the following condition: 1.5≤BF / fw≤1.8 Where BF is the back focal equivalent air length of the lens, and fw is the focal length of the lens at the wide-angle end.

3. The large aperture zoom projection lens according to claim 1, characterized in that, During the focusing process from infinity to close distance on the magnifying side of the lens, the second lens group (200) moves along the optical axis from the shrinking side toward the magnifying side.

4. The large aperture zoom projection lens according to claim 1, characterized in that, During the zoom process from short to long effective focal length, the third lens group (300) moves along the optical axis from the magnification side to the reduction side.

5. The large aperture zoom projection lens according to claim 1, characterized in that, During the zoom process of the lens from short to long effective focal length, there are a first zoom segment and a second zoom segment. In the first zoom segment, the fourth lens group (400) moves along the optical axis from the shrinking side to the magnifying side. In the second zoom segment, the fourth lens group (400) moves along the optical axis from the magnifying side to the shrinking side.

6. The large aperture zoom projection lens according to claim 1, characterized in that, During the zoom process from short to long effective focal length, the fifth lens group (500) moves along the optical axis from the shrinking side to the magnifying side.

7. The large aperture zoom projection lens according to claim 1, characterized in that, During the zoom process from short to long effective focal length, the sixth lens group (600) moves along the optical axis from the shrinking side to the magnifying side.

8. The large aperture zoom projection lens according to claim 1, characterized in that, The aperture of the lens remains constant during zooming.

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