A long-focus continuous zoom projection lens with a wide focusing range

Abstract

The application discloses a long-focus continuous zoom projection lens capable of wide-range focusing, which sequentially comprises a focusing group, a zoom group and a fixed group from an object side to an image side, the focusing group comprises a first lens group and a second lens group, the zoom group comprises a third lens group to a sixth lens group, the fixed group comprises a seventh lens group, an aperture is arranged before the fifth lens group, the first lens group has positive refractive power, the second lens group has positive refractive power, the third lens group has negative refractive power, the fourth lens group has positive refractive power, the fifth lens group has positive refractive power, the sixth lens group has positive refractive power, and the seventh lens group has positive refractive power. The embodiment of the application keeps the picture clear during wide-range focusing, is compatible with various application scenarios, and can be widely applied to optical systems.

Description

Technical Field

[0001] This invention relates to optical systems, and more particularly to a long-focal-length continuous zoom projection lens capable of focusing over a wide range. Background Technology

[0002] Projectors are characterized by large screen size and wide range of applications, and their share in the display field is increasing. Most projectors on the market are short-throw or ultra-short-throw projectors, which are mainly suitable for home theaters, while long-throw projectors are relatively less common and are mainly used for large-scale performances, exhibitions, and conferences. The clarity of projectors on the market can only meet the needs of one of these application scenarios, which limits their application scope. Summary of the Invention

[0003] In view of this, the purpose of this invention is to provide a long-focus continuous zoom projection lens that can maintain image clarity over a wide range of focusing areas and is compatible with various application scenarios.

[0004] This invention provides a long-focus continuous zoom projection lens with a wide focusing range. From the object side to the image side, it includes a focusing group, a zoom group, and a fixed group. The focusing group includes a first lens group and a second lens group. The zoom group includes a third to a sixth lens group. The fixed group includes a seventh lens group. An aperture stop is provided before the fifth lens group. The first lens group has positive optical power, the second lens group has positive optical power, the third lens group has negative optical power, the fourth lens group has positive optical power, the fifth lens group has positive optical power, the sixth lens group has positive optical power, and the seventh lens group has positive optical power.

[0005] Optionally, the first lens group includes a cemented doublet consisting of a first lens and a second lens, and the second lens group includes a third lens.

[0006] Optionally, the Abbe number of the lenses with positive optical power in the first lens group and the second lens group is between 55 and 75, and the Abbe number of the lenses with negative optical power is between 20 and 40.

[0007] Optionally, the first lens group and the second lens group satisfy the following relationship:

[0008] 1.0 <f1 / f2<3.0

[0009] Where f1 represents the focal length of the first lens group and f2 represents the focal length of the second lens group.

[0010] Optionally, the third lens group and the fourth lens group satisfy the following relationship:

[0011] -0.5 <f3 / f4<-0.1

[0012] Where f3 represents the focal length of the third lens group and f4 represents the focal length of the fourth lens group.

[0013] Optionally, the third lens group and the sixth lens group satisfy the following relationship:

[0014] -0.7 <f3 / f6<-0.1

[0015] Where f3 represents the focal length of the third lens group and f6 represents the focal length of the sixth lens group.

[0016] Optionally, the third lens group and the lens group behind the aperture satisfy the following relationship:

[0017] -0.7 <f3 / f8<-0.2

[0018] Where f3 represents the focal length of the third lens group, and f8 represents the focal length of the lens group behind the aperture stop.

[0019] Optionally, the third lens group includes the fourth to eighth lenses, the fourth lens group includes the ninth to tenth lenses, the fifth lens group includes the eleventh to seventeenth lenses, the sixth lens group includes the eighteenth lens, and the seventh lens group includes the nineteenth lens.

[0020] Optionally, all lenses in the projection lens may be made of all-glass material.

[0021] Optionally, all surfaces of all lenses in the projection lens are spherical.

[0022] Implementing the embodiments of the present invention has the following beneficial effects: The long-focal-length continuous zoom projection lens with a wide focusing range includes a focusing group, a zoom group, and a fixed group sequentially from the object side to the image side. The focusing group includes a first lens group and a second lens group, the zoom group includes a third to a sixth lens group, and the fixed group includes a seventh lens group. An aperture stop is provided before the fifth lens group. The embodiments of the present invention use the movement of two focusing groups to complete the focus adjustment. Compared with the focusing method of other projections using a single focusing group or the entire lens, the setting of two focusing groups increases the variables during lens focusing, which is more conducive to balancing the aberration differences caused by different projection distances. The focal length of the optical system of the embodiments of the present invention can range from 29.8mm to 5mm. A 2x zoom ratio is achieved through a continuous 9.6mm change, making it compatible with more application scenarios. It can maintain image clarity for projection distances from 2.5m to 50m and image sizes from 60 inches to 1000 inches. The lens structure of this embodiment is compact, with a total lens length of only 173mm. The use of four zoom groups helps to shorten the travel distance of the zoom group, thus achieving 2x zoom even with a shorter travel distance. The aperture in the lens moves with the fifth lens group of the zoom group. Due to the short travel distance of the zoom group, when the focal length changes from 29.8mm to 59.6mm, the F-number only changes from 2.0 to 2.2, ensuring that the brightness of the projected image does not change significantly during zooming. Attached Figure Description

[0023] Figure 1 This invention provides a long-focus continuous zoom projection lens with a wide focusing range.

[0024] Figure 2 A schematic diagram of the lens with focal lengths of 29.8mm and 59.6mm in Embodiment 1 provided for the present invention;

[0025] Figure 3 A schematic diagram of the lens in Embodiment 1 of the present invention with projection distances of 2.5m and 50m;

[0026] Figure 4 A schematic diagram of the MTF (Medium Flow Chart) when the focal length is 29.8mm in Embodiment 1 of this invention;

[0027] Figure 5 A schematic diagram of the MTF (Mean Transformer Format) when the focal length is 59.6mm in Embodiment 1 of this invention;

[0028] Figure 6 A schematic diagram of the MTF (Mean Transmission Flow) when the projection distance is 2.5m in Embodiment 1 of this invention;

[0029] Figure 7 This is a schematic diagram of the MTF (Mean Transmission Flow) when the projection distance is 50m in Embodiment 1 of the present invention.

[0030] Figure 8 A schematic diagram of the lens with focal lengths of 29.8mm and 59.6mm in Embodiment 2 provided for the present invention;

[0031] Figure 9 A schematic diagram of the lens in Embodiment 2 of the present invention with projection distances of 2.5m and 50m;

[0032] Figure 10 A schematic diagram of the MTF (Medium Flow Chart) when the focal length is 29.8mm in Embodiment 2 of this invention;

[0033] Figure 11 A schematic diagram of the MTF (Medium-to-Frequency Form) when the focal length is 59.6mm in Embodiment 2 of this invention;

[0034] Figure 12 A schematic diagram of the MTF (Mean Transformation Factor) when the projection distance is 2.5m in Embodiment 2 of this invention;

[0035] Figure 13 This is a schematic diagram of the MTF (Mean Transformation Factor) when the projection distance is 50m in Embodiment 2 of the present invention. Detailed Implementation

[0036] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. The step numbers in the following embodiments are only for ease of explanation and do not limit the order of the steps. The execution order of each step in the embodiments can be adapted according to the understanding of those skilled in the art.

[0037] like Figure 1 As shown, this embodiment of the invention provides a long-focus continuous zoom projection lens with a wide focusing range. From the object side to the image side, it includes a focusing group, a zoom group, and a fixed group. The focusing group includes a first lens group G1 and a second lens group G2. The zoom group includes a third to a sixth lens group (G3, G4, G5, G6). The fixed group includes a seventh lens group G7. An aperture stop STO is provided before the fifth lens group G5. The first lens group G1 has positive optical power, the second lens group G2 has positive optical power, the third lens group G3 has negative optical power, the fourth lens group G4 has positive optical power, the fifth lens group G5 has positive optical power, the sixth lens group G6 has positive optical power, and the seventh lens group G7 has positive optical power.

[0038] It should be noted that the lenses in each lens group of the focusing group, zoom group, and fixed group are determined according to the actual application, and this embodiment does not impose specific restrictions.

[0039] Optionally, see Figure 1The first lens group G1 includes a cemented doublet consisting of a first lens L1 and a second lens L2, and the second lens group G2 includes a third lens L3.

[0040] One of the focusing elements is a cemented doublet, which helps balance chromatic aberration and field curvature aberrations caused by focusing at different projection distances. Furthermore, the focusing group consists of only one cemented doublet lens and one lens with positive power, resulting in a simple focusing method.

[0041] It should be noted that the focusing group uses an "++" power distribution. When the projection distance changes, the first and second lens groups of the focusing group move in the same direction along the optical axis to achieve focusing, thereby making the projected image clear.

[0042] Optionally, the Abbe number of the lens with positive optical power in the first lens group and the second lens group is between 55 and 75, and the Abbe number of the lens with negative optical power is between 20 and 40.

[0043] It should be noted that the Abbe number of each lens in the first lens group and the second lens group is determined according to the actual application, and this embodiment does not impose specific restrictions.

[0044] Optionally, see Figure 1 The third lens group G3 includes the fourth to eighth lenses (L4, L5, L6, L7, L8), the fourth lens group G4 includes the ninth lens L9 to the tenth lens L10, the fifth lens group G5 includes the eleventh to the seventeenth lenses (L9, L10, L11, L12, L13, L14, L15, L16, L17), the sixth lens group G6 includes the eighteenth lens L18, and the seventh lens group G7 includes the nineteenth lens L19.

[0045] It should be noted that the thirteenth and fourteenth lenses are cemented lenses, as are the fifteenth, sixteenth, and seventeenth lenses.

[0046] Optionally, the first lens group and the second lens group satisfy the following relationship:

[0047] 1.0 <f1 / f2<3.0

[0048] Where f1 represents the focal length of the first lens group and f2 represents the focal length of the second lens group.

[0049] It should be noted that the focal length of the first lens group and the focal length of the second lens group are determined according to the actual application, and this embodiment does not impose specific limitations.

[0050] Optionally, the third lens group and the fourth lens group satisfy the following relationship:

[0051] -0.5 <f3 / f4<-0.1

[0052] Where f3 represents the focal length of the third lens group and f4 represents the focal length of the fourth lens group.

[0053] It should be noted that the focal lengths of the third lens group and the fourth lens group are determined according to the actual application, and this embodiment does not impose specific limitations.

[0054] Optionally, the third lens group and the sixth lens group satisfy the following relationship:

[0055] -0.7 <f3 / f6<-0.1

[0056] Where f3 represents the focal length of the third lens group and f6 represents the focal length of the sixth lens group.

[0057] It should be noted that the focal lengths of the third lens group and the sixth lens group are determined based on the actual application, and this embodiment does not impose specific limitations.

[0058] Optionally, the third lens group and the lens group behind the aperture stop satisfy the following relationship:

[0059] -0.7 <f3 / f8<-0.2

[0060] Where f3 represents the focal length of the third lens group, and f8 represents the focal length of the lens group behind the aperture stop.

[0061] It should be noted that the focal length of the third lens group and the focal length of the lens group behind the aperture stop are determined according to the actual application, and this embodiment does not impose specific limitations.

[0062] Optionally, all lenses in the projection lens may be made of all-glass material.

[0063] Optical glass is characterized by high transparency, purity, colorlessness, uniform texture, and excellent refractive ability. Optical glass includes the following types: flint glass—made by adding lead oxide to the glass composition to increase its refractive index; crown glass—made by adding sodium oxide and calcium oxide to the glass composition to reduce its refractive index; and lanthanum crown glass—possessing excellent properties of high refractive index and low dispersion, providing the conditions for creating large-aperture high-end lenses.

[0064] Optionally, all surfaces of all lenses in the projection lens are spherical.

[0065] Spherical lenses can improve spherical aberration and chromatic aberration, reduce aberrations, and improve image quality.

[0066] Example 1: The optical data of the projection lens are shown in Table 1. Where R represents the radius of curvature of the lens, d represents the lens thickness or air gap, n represents the refractive index of the glass, and v represents the Abbe number of the glass.

[0067] Table 1

[0068]

[0069]

[0070] See Figure 2 Example 1 provides lens diagrams for focal lengths of 29.8mm and 59.6mm. (See attached image.) Figure 3 Example 1 provides lens diagrams for projection distances of 2.5m and 50m. Air gap data from D0 to D7 are shown in Tables 2 and 3. Table 2 shows the changes in air gap between the focus groups at different projection distances. When the lens focal length is 29.8mm, a projection distance of 2.5m can project a 60-inch image, a projection distance of 5.2m can project a 120-inch image, suitable for smaller screens such as home theaters, and a projection distance of 50m can project a 1200-inch image, suitable for large performances, exhibitions, conferences, etc. Table 3 shows the changes in air gap between the zoom groups at different focal lengths, achieving 2x zoom.

[0071] Table 2

[0072] D0 2500 5200 50000 D1 11.21 4.39 0.20 D2 5.51 3.91 2.56

[0073] Table 3

[0074] focal length 29.8 59.6 D3 0.20 19.45 D4 12.18 0.20 D5 20.69 2.02 D6 20.91 17.20 D7 0.20 15.31

[0075] See Figures 4 to 7 According to the MTF curves of the imaging quality of different projection lenses in Example 1, it can be seen that... Figures 4-7 The various MTF curves represent the imaging quality of different fields of view. Figures 4-7 The vertical coordinate values ​​corresponding to 66 line pairs / mm on the horizontal axis are all above 0.68, indicating that the pixels can be clearly distinguished and the projected image quality reaches a high level.

[0076] Example 2, Optical Data Table 4 for the Projection Lens. Where R represents the radius of curvature of the lens, d represents the lens thickness or air gap, n represents the refractive index of the glass, and v represents the Abbe number of the glass.

[0077] Table 4

[0078]

[0079]

[0080] See Figure 8 Example 2 provides lens diagrams for focal lengths of 29.8mm and 59.6mm. (See attached image.) Figure 9Example 2 provides lens diagrams for projection distances of 2.5m and 50m. Air gap data from D0 to D7 are shown in Tables 5 and 6. Table 5 shows the changes in air gap between the focus groups at different projection distances. When the lens focal length is 29.8mm, a projection distance of 2.5m can project a 60-inch image, a projection distance of 5.2m can project a 120-inch image, suitable for smaller screens such as home theaters, and a projection distance of 50m can project a 1200-inch image, suitable for large performances, exhibitions, conferences, etc. Table 6 shows the changes in air gap between the zoom groups at different focal lengths, achieving 2x zoom.

[0081] Table 5

[0082] D0 2500 5200 50000 D1 17.08 6.46 0.20 D2 4.49 2.73 1.27

[0083] Table 6

[0084] focal length 29.8 59.6 D3 4.6 24.4 D4 22.5 0.2 D5 15.6 6.2 D6 18.9 18.6 D7 0.5 12.7

[0085] See Figures 10 to 12 According to the MTF curves of the imaging quality of different projection lenses in Example 2, it can be seen that... Figures 10-12 The various MTF curves represent the imaging quality of different fields of view. Figures 10-12 The vertical coordinate values ​​corresponding to 66 line pairs / mm on the horizontal axis are all above 0.6, indicating that the pixels can be clearly distinguished and the projected image quality reaches a high level.

[0086] Implementing the embodiments of the present invention has the following beneficial effects: The long-focal-length continuous zoom projection lens with a wide focusing range includes a focusing group, a zoom group, and a fixed group sequentially from the object side to the image side. The focusing group includes a first lens group and a second lens group, the zoom group includes a third to a sixth lens group, and the fixed group includes a seventh lens group. An aperture stop is provided before the fifth lens group. The embodiments of the present invention use the movement of two focusing groups to complete the focus adjustment. Compared with the focusing method of other projections using a single focusing group or the entire lens, the setting of two focusing groups increases the variables during lens focusing, which is more conducive to balancing the aberration differences caused by different projection distances. The focal length of the optical system of the embodiments of the present invention can range from 29.8mm to 5mm. A 2x zoom ratio is achieved through a continuous 9.6mm change, making it compatible with more application scenarios. It can maintain image clarity for projection distances from 2.5m to 50m and image sizes from 60 inches to 1000 inches. The lens structure of this embodiment is compact, with a total lens length of only 173mm. The use of four zoom groups helps to shorten the travel distance of the zoom group, thus achieving 2x zoom even with a shorter travel distance. The aperture in the lens moves with the fifth lens group of the zoom group. Due to the short travel distance of the zoom group, when the focal length changes from 29.8mm to 59.6mm, the F-number only changes from 2.0 to 2.2, ensuring that the brightness of the projected image does not change significantly during zooming.

[0087] The above is a detailed description of the preferred embodiments of the present invention. However, the present invention is not limited to the embodiments described. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present invention. All such equivalent modifications or substitutions are included within the scope defined by the claims of this application.

Claims

1. A long-focal-length continuous zoom projection lens capable of focusing over a wide range, characterized in that, From object side to image side, the system sequentially includes a focusing group, a zoom group, and a fixed group. The focusing group includes a first lens group and a second lens group. The zoom group includes a third to a sixth lens group. The fixed group includes a seventh lens group. An aperture stop is provided before the fifth lens group. The first lens group has positive optical power, the second lens group has positive optical power, the third lens group has negative optical power, the fourth lens group has positive optical power, the fifth lens group has positive optical power, the sixth lens group has positive optical power, and the seventh lens group has positive optical power. The first lens group includes a cemented doublet composed of a first lens and a second lens. The second lens group includes a third lens. The third lens group includes a fourth to a eighth lens. The fourth lens group includes a ninth to a tenth lens. The fifth lens group includes an eleventh to a seventeenth lens. The sixth lens group includes an eighteenth lens. The seventh lens group includes a nineteenth lens.

2. The projection lens according to claim 1, characterized in that, The Abbe number of the lenses with positive optical power in the first lens group and the second lens group is between 55 and 75, and the Abbe number of the lenses with negative optical power is between 20 and 40.

3. The projection lens according to claim 1, characterized in that, The first lens group and the second lens group satisfy the following relationship: 1.0< f 1 / f 2<3.0 in, f 1 represents the focal length of the first lens group. f 2 represents the focal length of the second lens group.

4. The projection lens according to claim 1, characterized in that, The third lens group and the fourth lens group satisfy the following relationship: -0.5< f 3 / f 4<-0.1 in, f 3 indicates the focal length of the third lens group. f 4 indicates the focal length of the fourth lens group.

5. The projection lens according to claim 1, characterized in that, The third lens group and the sixth lens group satisfy the following relationship: -0.7< f 3 / f 6<-0.1 in, f 3 indicates the focal length of the third lens group. f 6 indicates the focal length of the sixth lens group.

6. The projection lens according to claim 1, characterized in that, The third lens group and the lens group behind the aperture satisfy the following relationship: -0.7< f 3 / f 8<-0.2 in, f 3 indicates the focal length of the third lens group. f 8 indicates the focal length of the lens group behind the aperture stop.

7. The projection lens according to claim 1, characterized in that, All lenses in the projection lens are made of glass.

8. The projection lens according to claim 1, characterized in that, All lenses in the projection lens have spherical surfaces.

Images