A wide-angle zoom anamorphic widescreen lens

Abstract

The present invention discloses a wide-angle zoom anamorphic widescreen lens. The lens is composed, from the object side to the image side, of a first lens group G1 with negative refractive power, a cylindrical lens anamorphic group G2, a fixed lens group G3, a fourth lens group G4, a fifth lens group G5, a sixth lens group G6, and a sixth lens group G7. The first lens group G1 comprises a front portion G1a with negative refractive power and a rear portion G1b with negative refractive power. When an object moves from infinity to a close distance to achieve focus, G1b moves toward the object side to achieve focus. The present invention provides a high-performance, compact zoom anamorphic widescreen lens with a zoom ratio exceeding 1.5x and an anamorphic ratio of 1.5 to 2x. Furthermore, the lens has a horizontal viewing angle exceeding 65° at the wide-angle end. After deformation, the image is decompressed again, and the blurred light spot presents an elliptical shape, meeting the artistic requirement.

Description

Technical Field

[0001] The present invention is a digital camera lens with anamorphic widescreen function, in particular a wide-angle zoom anamorphic lens with a vertical and horizontal anamorphic ratio of more than 1.5 times, and provides good optical performance. Background Art

[0002] With the advancement of high-definition movie cameras in recent years, the increasingly popular digital camera systems mostly use 3:2 and 16:9 formats. However, cinema screens are mostly 2.35:1, 2.6:1, or even larger. Therefore, during playback, the film needs to be cropped up and down to achieve this aspect ratio to meet the visual habits of the human eye. This cropping results in a significant loss of effective pixels, reducing image quality. As a result, the market demand for high-performance, high-compression anamorphic lenses is increasing. At the same time, the filming process requires lenses of various focal lengths, which requires constant lens switching, which is very cumbersome and inefficient. Therefore, the demand for zoom anamorphic lenses is very urgent.

[0003] Currently known patents for zoom anamorphic widescreen lenses, such as those described in Japanese Patent Laid-Open No. 6-82691, place a cylindrical lens anamorphic group at the front of a conventional zoom optical system. While this achieves the desired zoom anamorphic effect, simply placing the anamorphic group at the front results in very poor close-range performance. Furthermore, focusing behind the anamorphic group, i.e., within the zoom lens, makes parfocality difficult to achieve. Furthermore, the placement of the cylindrical lens at the front of the anamorphic group inevitably results in a bulky, heavy, and expensive manufacturing process. This is especially true for very wide-angle zoom lenses, making it difficult to achieve an anamorphic ratio of 1.5x or even 2x.

[0004] For example, as described in the well-known Japanese Patent Laid-Open No. 2005-221597, Example 1 also places a cylindrical lens group with a 1.33x distortion ratio between the aperture and the image plane of the zoom lens. Although this can achieve the zoom distortion effect, the distortion ratio is also small, and the elliptical spot cannot be obtained to meet the artistic creation requirements. Example 2 places the cylindrical lens with distortion at the very front end of the zoom lens. However, due to the characteristics of the cylindrical lens, the focal lengths in the horizontal X direction and the vertical Y direction are different. When placed at the very front end, although the image point position can be consistent at infinity and a good imaging effect can be achieved, when the object moves to a certain close distance, the different focal lengths in the X and Y directions inevitably lead to different image point positions. Once the depth of field range is exceeded, the performance of the X and Y directions is easily caused to drop sharply due to the inconsistent image point positions. Therefore, the close-up performance of this structure is very poor. Summary of the Invention

[0005] To overcome the technical problems of conventional zoom anamorphic lenses, such as low distortion ratio, performance degradation as object distance changes, and bulkiness, the present invention provides a high-performance wide-angle zoom anamorphic lens with a length-to-width distortion ratio of 1.5x or greater and a zoom ratio of 1.5x or greater.

[0006] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical solutions:

[0007] The present invention provides a wide-angle zoom anamorphic wide-screen lens, which is composed of, from the object side to the image side, a first lens group G1 with negative refractive power, a cylindrical lens anamorphic group G2, a fixed lens group G3, a fourth lens group G4, a fifth lens group G5, a sixth lens group G6, and a sixth lens group G7;

[0008] illustrate:

[0009] Furthermore, the wide-angle zoom anamorphic lens satisfies the following conditions:

[0010] 6≤|L / Wfy|≤12 (1)

[0011] in,

[0012] L: The length of the entire optical system.

[0013] Wfy: The Y-direction focal length of the optical system at the wide-angle end at infinity.

[0014] Further technology of the present invention:

[0015] Preferably, the first lens group G1 consists of a front portion G1a with negative refractive power and a rear portion G1b with negative refractive power; and the first lens group G1 satisfies the following conditional formula:

[0016] 1.5≤|F1 b / F1|≤2.5 (2)

[0017] Wherein, F1b: focal length of the negative refractive power rear portion G1b of the first lens group G1;

[0018] F1: Focal length of the first lens group G1 at infinity.

[0019] Preferably, the cylindrical lens deformation group G2 consists of a Y-direction cylindrical lens group Y and an X-direction cylindrical lens group X, wherein the Y-direction cylindrical lens group consists of a positive refractive power Ya and a negative refractive power Yb; and the cylindrical lens deformation group G2 satisfies the following conditional formula:

[0020] 1.5≤|Fyb / Fya|≤2.2 (3)

[0021] 2.1≤|Fya / WFy|≤2.8 (4)

[0022] 1≤|Fya / DY|≤3 (5)

[0023] in,

[0024] Fya: Focal length of the Y-direction cylindrical lens group with positive refractive power Ya;

[0025] Fyb: focal length of the Y-direction cylindrical lens group with negative refractive power Yb;

[0026] DY: The length of the cylindrical mirror group in the Y direction of the cylindrical mirror deformation group G2.

[0027] Preferably, the fourth lens group G4 satisfies the following conditional formula:

[0028] 1≤F4 / Wfy≤2 (6)

[0029] 0.1≤F4 / L≤0.22 (7)

[0030] in,

[0031] F4: Focal length of the fourth lens group G4.

[0032] Preferably, the fifth lens group G5 satisfies the following conditional formula:

[0033] 0.2≤|F4 / F5|≤1.5 (8)

[0034] in,

[0035] F5: Focal length of the fifth lens group G5.

[0036] Preferably, zooming is achieved by moving the fourth lens group G4, the fifth lens group G5 and the sixth lens group G6. During zooming, the movement amounts of the fourth lens group G4, the fifth lens group G5 and the sixth lens group G6 satisfy the following conditional formula:

[0037] 5≤L / (S4+S5+S6)≤12 (8)

[0038] S4: Movement of the fourth lens group G4 from the wide-angle end to the telephoto end.

[0039] S5: Movement of the fifth lens group G5 from the wide-angle end to the telephoto end.

[0040] S6: Movement of the sixth lens group G6 from the wide-angle end to the telephoto end.

[0041] The beneficial effect of the present invention is to provide a high-performance, small-sized zoom anamorphic wide-screen lens with a zoom ratio exceeding 1.5 times and an deformation ratio of 1.5 to 2 times, and a wide-angle zoom lens with a horizontal viewing angle exceeding 65° at the wide-angle end. After deformation, the image is decompressed again, and the blurred light spot presents an elliptical artistic requirement. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 1 is a structural diagram of the wide-angle end and the telephoto end of a YZ view in accordance with an embodiment of the present invention;

[0043] Figure 2 The spherical aberration, field curvature aberration, distortion aberration, and chromatic aberration of magnification in the Y and X directions at infinity and close distance at the wide-angle end, intermediate focal length, and telephoto end of the first embodiment;

[0044] Figure 3 1 is a structural diagram of the wide-angle end and the telephoto end of the YZ view of the second embodiment of the present invention;

[0045] Figure 4 The spherical aberration, field curvature, distortion, and chromatic aberration of magnification in the Y and X directions at infinity and close distances at the wide-angle end, intermediate focal length, and telephoto end of Example 2;

[0046] Figure 5 1 is a structural diagram of the wide-angle end and the telephoto end of the YZ view of the third embodiment of the present invention;

[0047] Figure 6 These are the spherical aberration, field curvature aberration, distortion aberration, and chromatic aberration of magnification in the Y and X directions at infinity and close distance at the wide-angle end, intermediate focal length, and telephoto end of Example 3. DETAILED DESCRIPTION

[0048] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0049] A wide-angle zoom anamorphic widescreen lens comprises, from the object side to the image side, a first lens group G1 with negative refractive power, an anamorphic group G2, a fixed group G3, an aperture stop, a zoom movable group (a fourth lens group G4), a fifth lens group G5, a sixth lens group G6, and a fixed group (a seventh lens group G7). The first lens group comprises a front portion G1a with negative refractive power and a rear portion G1b with negative refractive power. When an object moves from infinity to a close distance to achieve focus, G1b moves toward the object side to achieve focus.

[0050] illustrate:

[0051] It should be noted that a wide-angle zoom anamorphic lens satisfies the following conditions:

[0052] 6≤|L / Wfy|≤12 (1)

[0053] in,

[0054] L: The length of the entire optical system.

[0055] Wfy: The Y-direction focal length of the optical system at the wide-angle end at infinity.

[0056] If the lower limit of the conditional expression 6≤|L / Wfy|≤12(1) is exceeded, although the entire optical system can be made very small, the focal length at the wide-angle end will be too long, making it difficult to achieve a horizontal viewing angle of more than 65°, and wide-angle zoom will be difficult to achieve.

[0057] If the upper limit of conditional expression (1) is exceeded, a horizontal viewing angle of 65° or more can be easily achieved, but the length L of the lens is too long, making miniaturization difficult.

[0058] It should be noted that the first lens group G1 consists of a front portion G1a with negative refractive power and a rear portion G1b with negative refractive power; and the first lens group G1 satisfies the following conditional formula:

[0059] 1.5≤|F1 b / F1|≤2.5 (2)

[0060] Wherein, F1b: focal length of the negative refractive power rear portion G1b of the first lens group G1;

[0061] F1: Focal length of the first lens group G1 at infinity.

[0062] If the lower limit of the conditional expression 1.5≤|F1 b / F1|≤2.5(2) is exceeded, the refractive power of the rear portion G1 b of the first group G1 becomes too strong. While close-range focusing can be easily achieved, the excessive refractive power makes it difficult to correct various aberrations, making high performance difficult.

[0063] If the lower limit of conditional expression (2) is exceeded, the refractive power of G1b is weak. Although high performance can be easily achieved, close-up distance is difficult to achieve and the focusing distance becomes very long. This will also cause the entire optical system to become larger and miniaturization will also be difficult.

[0064] It should be noted that the cylindrical lens deformation group G2 consists of a Y-direction cylindrical lens group Y and an X-direction cylindrical lens group X, wherein the Y-direction cylindrical lens group consists of a positive refractive power Ya and a negative refractive power Yb; and the cylindrical lens deformation group G2 satisfies the following conditional formula:

[0065] 1.5≤|Fyb / Fya|≤2.2 (3)

[0066] 2.1≤|Fya / WFy|≤2.8 (4)

[0067] 1≤|Fya / DY|≤3 (5)

[0068] in,

[0069] Fya: Focal length of the Y-direction cylindrical lens group with positive refractive power Ya;

[0070] Fyb: focal length of the Y-direction cylindrical lens group with negative refractive power Yb;

[0071] DY: The length of the cylindrical mirror group in the Y direction of the cylindrical mirror deformation group G2.

[0072] If the lower limit of the conditional expression 1.5≤|Fyb / Fya|≤2.2(3) is exceeded, the refractive power of the front portion Ya of the cylindrical lens group in the Y direction is weak, making it very difficult to achieve a distortion ratio of 1.5 times or more within a limited space. If a distortion ratio of 1.5 times or more is achieved, the volume will increase. If the upper limit of the conditional expression (3) is exceeded, the refractive power of the front portion Ya of the cylindrical lens group in the Y direction becomes very strong. Although distortion ratios of 1.5 times and 2 times can be achieved in a small volume, the strong refractive power will cause various aberrations to increase sharply, making it difficult to correct and achieve high performance.

[0073] If the lower limit of the conditional expression 2.1 ≤ |Fya / WFy| ≤ 2.8 (4) is exceeded, the refractive power of the front portion Ya of the Y-direction cylindrical lens group is too strong. Although it is easy to achieve a wide-angle and high distortion ratio effect, it is difficult to correct aberrations and achieve high performance. If the upper limit of the conditional expression (4) is exceeded, the refractive power of the front portion Ya of the Y-direction cylindrical lens group is too weak. Although it is easy to achieve high performance, it is difficult to achieve a viewing angle of more than 65° and a distortion ratio of more than 1.5 times, and miniaturization is also difficult to achieve.

[0074] If the lower limit of the conditional expression 1≤|Fya / DY|≤3(5) is exceeded, the refractive power of the front part Ya of the Y-direction cylindrical lens group is too strong relative to the volume. Although it is easy to achieve a high deformation ratio of 1.5 times and 2 times, the strong refractive power will cause a sharp increase in aberrations, making it difficult to achieve high performance. Alternatively, the refractive power of Ya is moderate, but the cylindrical lens group DY in the Y-direction is too long. Although it is also easy to achieve a high deformation ratio, the volume is too large and it is difficult to achieve miniaturization. If the upper limit of the conditional expression (5) is exceeded, the refractive power of the front part Ya of the Y-direction cylindrical lens group is too weak relative to the volume. Although it is easy to achieve high performance, it is difficult to achieve a deformation ratio of more than 1.5 times. Alternatively, the refractive power of Ya is moderate, but the length of the cylindrical lens group DY in the Y-direction is too short. Although miniaturization is easy to achieve, the small volume makes it difficult to achieve a deformation ratio of more than 1.5 times.

[0075] It should be noted that the fourth lens group G4 satisfies the following conditional formula:

[0076] 1≤F4 / Wfy≤2 (6)

[0077] 0.1≤F4 / L≤0.22 (7)

[0078] in,

[0079] F4: Focal length of the fourth lens group G4.

[0080] If the lower limit of the conditional expression 1 ≤ F4 / Wfy ≤ 2 (6) is exceeded, the refractive power of the fourth lens group G4 is too strong. Although a zoom effect can be achieved with a small movement, the strong refractive power will lead to a significant increase in various aberrations. At the same time, the sensitivity will be too high, making mass production very difficult. If the upper limit of the conditional expression (6) is exceeded, the refractive power of the fourth lens group G4 is too weak. If a suitable zoom ratio is to be achieved, the movement will increase. Although the performance is easy to achieve, the volume will become large, making miniaturization more difficult.

[0081] If the lower limit of the conditional expression 0.1 ≤ F4 / L ≤ 0.22 (7) is exceeded, the refractive power of the fourth lens group G4 is too strong. Although the zoom effect can be achieved with a small movement, the strong refractive power will lead to a significant increase in various aberrations. At the same time, the sensitivity will be too high, and mass production will become very difficult. If the upper limit of the conditional expression (7) is exceeded, the refractive power of the fourth lens group G4 is too weak. If a suitable zoom ratio is to be achieved, the movement amount will increase. Although the performance is easy to achieve, the volume will become large, making miniaturization more difficult.

[0082] It should be noted that the fifth lens group G5 satisfies the following conditional formula:

[0083] 0.2≤|F4 / F5|≤1.5 (8)

[0084] in,

[0085] F5: Focal length of the fifth lens group G5.

[0086] If the lower limit of the conditional expression 0.2 ≤ |F4 / F5| ≤ 1.5 (9) is exceeded, the refractive power of the fourth lens group G4 is too strong. Although a suitable zoom ratio can be achieved with a small amount of movement, various aberrations tend to increase significantly due to the high refractive power, making it difficult to achieve high performance. At the same time, the sensitivity is also very high, making mass production difficult. Conversely, if the upper limit of the conditional expression (9) is exceeded, the refractive power of the fourth lens group G4 is too weak. Although high performance can be achieved, it is difficult to achieve a suitable zoom ratio within a limited space.

[0087] It should be noted that zooming is achieved by moving the fourth lens group G4, the fifth lens group G5 and the sixth lens group G6. During zooming, the movement amounts of the fourth lens group G4, the fifth lens group G5 and the sixth lens group G6 satisfy the following conditional formula:

[0088] 5≤L / (S4+S5+S6)≤12 (8)

[0089] S4: Movement of the fourth lens group G4 from the wide-angle end to the telephoto end.

[0090] S5: Movement of the fifth lens group G from the wide-angle end to the telephoto end.

[0091] S6: Movement of the sixth lens group G6 from the wide-angle end to the telephoto end.

[0092] If the lower limit of the conditional expression 5≤L / (S4+S5+S6)≤12(8) is exceeded, the movement of the lens groups G4, G5, and G6 during zooming is too large. Although it is easy to achieve a zoom ratio, the volume of the anamorphic combination focus group is compressed, which makes it difficult to achieve an anamorphic ratio of more than 1.5 times. At the same time, the movement of the focus group is too small, resulting in poor close-up capability. If the upper limit of the conditional expression (8) is exceeded, the movement of the lens groups G4, G5, and G6 during zooming is too small, making it difficult to achieve a suitable zoom ratio in a limited space.

[0093] Three embodiments are provided below:

[0094] Example 1

[0095] like Figure 1 The structural diagram of the wide-angle end and the telephoto end of the YZ view shown in the figure includes, from the object side to the image side, the first lens group G1 with negative refractive power, the anamorphic group G2, the fixed group G3, the aperture stop, the zoom movable group fourth lens group G4, the fifth lens group G5, the sixth lens group G6 and the fixed group seventh lens group G7. The above-mentioned first lens group consists of a front part G1a with negative refractive power and a rear part G1b with negative refractive power. When the object moves from infinity to a close distance to achieve focus, G1b moves toward the object side to achieve focus.

[0096] like Figure 2 The spherical aberration, field curvature, distortion, and lateral chromatic aberration in the Y and X directions at infinity and near distances at the wide-angle end, intermediate focal length, and telephoto end of the first embodiment are shown.

[0097] [The data of Example 1 are as follows]

[0098] Rx (mm): Radius of curvature of each surface in the X direction

[0099] Ry(mm): Radius of curvature of each surface in the Y direction

[0100] D(mm): The distance between each lens and the thickness of the lens

[0101] Nd: Refractive index of each glass at the d line

[0102] Vd: Abbe number of glass

[0103]

[0104]

[0105]

[0106]

[0107]

[0108]

[0109]

[0110] Example 2

[0111] like Figure 3 The structural diagram of the wide-angle end and the telephoto end of the YZ view shown in the figure includes, from the object side to the image side, the first lens group G1 with negative refractive power, the anamorphic group G2, the fixed group G3, the aperture stop, the zoom movable group fourth lens group G4, the fifth lens group G5, the sixth lens group G6 and the fixed group seventh lens group G7. The above-mentioned first lens group consists of a front part G1a with negative refractive power and a rear part G1b with negative refractive power. When the object moves from infinity to a close distance to achieve focus, G1b moves toward the object side to achieve focus.

[0112] like Figure 4 The spherical aberration, field curvature, distortion, and lateral chromatic aberration in the Y and X directions at infinity and near distances at the wide-angle end, intermediate focal length, and telephoto end of the second embodiment are shown.

[0113] [The data of Example 2 are as follows]

[0114] Rx (mm): Radius of curvature of each surface in the X direction

[0115] Ry(mm): Radius of curvature of each surface in the Y direction

[0116] D(mm): The distance between each lens and the thickness of the lens

[0117] Nd: Refractive index of each glass at the d line

[0118] Vd: Abbe number of glass

[0119]

[0120]

[0121]

[0122]

[0123]

[0124]

[0125] Example 3

[0126] like Figure 5 The structural diagram of the wide-angle end and the telephoto end of the YZ view shown in the figure includes, from the object side to the image side, the first lens group G1 with negative refractive power, the anamorphic group G2, the fixed group G3, the aperture stop, the zoom movable group fourth lens group G4, the fifth lens group G5, the sixth lens group G6 and the fixed group seventh lens group G7. The above-mentioned first lens group consists of a front part G1a with negative refractive power and a rear part G1b with negative refractive power. When the object moves from infinity to a close distance to achieve focus, G1b moves toward the object side to achieve focus.

[0127] like Figure 6 The spherical aberration, field curvature, distortion, and lateral chromatic aberration in the Y and X directions at infinity and near distances at the wide-angle end, intermediate focal length, and telephoto end of the third embodiment are shown.

[0128] [The data of Example 3 are as follows]

[0129] Rx (mm): Radius of curvature of each surface in the X direction

[0130] Ry(mm): Radius of curvature of each surface in the Y direction

[0131] D(mm): The distance between each lens and the thickness of the lens

[0132] Nd: Refractive index of each glass at the d line

[0133] Vd: Abbe number of glass

[0134]

[0135]

[0136]

[0137]

[0138]

[0139]

[0140] (Conditional summary table)

[0141] Conditional expression Example 1 Example 2 Example 3 1 6≤|L / Wfy|≤12 9.119 8.435 9.202 2 1.5≤|F1b / F1|≤2.5 1.823 1.446 2.266 3 1.5≤|Fyb / Fya|≤2.2 1.838 1.777 2.042 4 2.1≤|Fya / WFy|≤2.8 2.532 2.420 2.489 5 1≤|Fya / DY|≤3 2.700 2.397 1.215 6 1≤F4 / Wfy≤2 1.306 1.310 1.798 7 0.1≤F4 / L≤0.22 0.143 0.155 0.195 8 0.2≤|F4 / F5|≤1.5 0.407 0.417 1.088 9 5≤L / (S4+S5+S6)≤12 7.492 6.552 9.513

[0142] The above content is merely an example and explanation of the structure of the present invention. Those skilled in the art may make various modifications or additions to the described specific embodiments or replace them in a similar manner. As long as they do not deviate from the structure of the invention or exceed the scope defined by the claims, they should all fall within the scope of protection of the present invention.

Claims

1. A wide-angle zoom anamorphic lens, characterized in that: From the object side to the image side, it consists of the first lens group G1 with negative refractive power, the cylindrical lens anamorphic group G2, the fixed lens group G3, the fourth lens group G4, the fifth lens group G5, the sixth lens group G6 and the seventh lens group G7. Furthermore, the wide-angle zoom anamorphic lens satisfies the following conditions: 6≤|L / Wfy|≤12 (1) in, L: length of the entire optical system; Wfy: The Y-direction focal length of the optical system at the wide-angle end at infinity; The first lens group G1 consists of a front portion G1a with negative refractive power and a rear portion G1b with negative refractive power; and the first lens group G1 satisfies the following conditional formula: 1.5≤|F1b / F1|≤2.5 (2) Wherein, F1b: focal length of the negative refractive power rear portion G1b of the first lens group G1; F1: focal length of the first lens group G1 at infinity; The cylindrical lens deformation group G2 is composed of a Y-direction cylindrical lens group Y and an X-direction cylindrical lens group X, wherein the Y-direction cylindrical lens group is composed of positive refractive power Ya and negative refractive power Yb; and the cylindrical lens deformation group G2 satisfies the following conditional formula: 1.5≤|Fyb / Fya|≤2.2 (3) 2.1≤|Fya / WFy|≤2.8 (4) 1≤|Fya / DY|≤3 (5) in, Fya: Focal length of the Y-direction cylindrical lens group with positive refractive power Ya; Fyb: focal length of the Y-direction cylindrical lens group with negative refractive power Yb; DY: The length of the cylindrical mirror group in the Y direction of the cylindrical mirror deformation group G2; The fourth lens group G4 satisfies the following conditional formula: 1≤F4 / Wfy≤2 (6) 0.1≤F4 / L≤0.22 (7) in, F4: focal length of the fourth lens group G4; The fifth lens group G5 satisfies the following conditional formula: 0.2≤|F4 / F5|≤1.5 (8) in, F5: focal length of the fifth lens group G5; Zooming is achieved by moving the fourth lens group G4, the fifth lens group G5, and the sixth lens group G6. During zooming, the movement amounts of the fourth lens group G4, the fifth lens group G5, and the sixth lens group G6 satisfy the following conditional formula: 5≤L / (S4+S5+S6)≤12 (9) S4: Movement of the fourth lens group G4 from the wide-angle end to the telephoto end; S5: Movement of the fifth lens group G5 from the wide-angle end to the telephoto end; S6: Movement of the sixth lens group G6 from the wide-angle end to the telephoto end.

Images