High-magnification wide-angle zoom lens

Abstract

The invention discloses a high-magnification wide-angle zoom lens, which relates to the field of broadcast zoom lenses for rebroadcasting, and sequentially comprises a first lens group G1 with positive diopter, a second lens group G2 with negative diopter, a third lens group G3 with negative diopter, a fourth lens group G4 with positive diopter and a fifth lens group G5 with positive diopter from an object side to an image surface side, and a sixth lens group G6 with negative diopter. The aperture Stop is arranged between the third lens group G3 and the fourth lens group G4; the first lens group G1 and the sixth lens group G6 are respectively fixed, and the second lens group G2, the third lens group G3, the fourth lens group G4 and the fifth lens group G5 are respectively moved to realize zooming from a wide-angle end to a telephoto end. The lens provided by the invention is reasonable in structure, high in performance, small in size and low in cost, the zoom ratio of more than 7 times can be realized, the field angle at the wide-angle end is greater than 90 degrees, and the picture diameter meets the sensor specification requirement of an S35 target surface.

Description

Technical Field

[0001] The present invention is a super wide-angle zoom lens with a zoom ratio exceeding 7 times and a wide-angle end field of view exceeding 90 degrees, which can be widely used in digital camera lenses, video camera lenses, and especially in the fields of broadcast-level zoom lenses for broadcasting. Background Art

[0002] At present, the image field of broadcast-level super zoom lenses for broadcasting is mostly 2 / 3-inch target surface. Although the lens is compact and has a high zoom ratio, it is difficult to achieve high pixel and high sensitivity requirements due to the small target surface of the image sensor, especially the large target surface and ultra-high-definition 8k sensors launched in recent years, with target surface sizes of mostly 1.25 inches and S35 specifications. For example, the well-known Japanese patent No. 2015-18083 has a structure that starts from one side of the object, when zooming, the first group is fixed with positive refractive power, and the second group with negative refractive power, the third group with negative refractive power, the fourth group with negative refractive power, and the fifth group with fixed positive refractive power are moved separately. When the object moves from infinity to close distance, the focusing group is the middle part of the first group, which moves toward the image plane to focus. When the imaging diameter meets the S35 specification, the zoom ratio is about 7 times, but the field of view is less than 80 degrees, and the field of view at the wide-angle end is insufficient. When the image field diameter only meets the 2 / 3-inch sensor, although the magnification can reach more than 10 times and the market angle can reach more than 90 degrees, the frame is too small to meet the current S35 specification sensor requirements. If the geometry is enlarged to the S35 specification requirements, the lens will be very large and bulky, and it will be difficult to put into practical use.

[0003] There is also the well-known Japanese patent No. 2020-160264, which has a structure that, starting from one side of the object, the first group of positive refractive power and the fifth group of positive refractive power are fixed when zooming, and the second group of negative refractive power, the third lens group of positive refractive power, and the fourth group of positive refractive power are moved respectively; when the object moves from infinity to close distance, the focusing group is the middle part of the first group of positive refractive power, which moves toward the image plane to focus. It can be seen from the embodiments that the zoom ratio is about 3 to 4 times, and the field of view at the wide-angle end is about 80 degrees. Although the image field can cover the full frame and the target surface diameter reaches more than 43mm, the volume is very large, but it cannot meet the high-magnification zoom requirements of more than 90 degrees at the wide-angle end and the zoom ratio cannot reach more than 7 times.

[0004] In summary, some of the currently known wide-angle zoom lenses, while achieving a zoom ratio of more than 7 times, a wide-angle field of view of more than 90 degrees, and an image field diameter that meets the requirements of the S35 frame, will become very large in size, with high manufacturing costs and great production difficulties, and cannot be mass-produced and popularized. It is difficult to achieve a zoom ratio of more than 7 times and a wide-angle field of view of more than 90 degrees while meeting the S35 image field specification. If this is to be achieved, the size of the lens will also become very large, and it is impossible to achieve low cost and mass production. Summary of the invention

[0005] In order to overcome the shortcomings of the above-mentioned known zoom lenses, the present invention provides a super wide-angle zoom lens solution with reasonable structure, high performance, small size and low cost, which can achieve a zoom ratio of more than 7 times, and the field of view at the wide-angle end is greater than 90 degrees, and the frame diameter meets the sensor specification requirements of the S35 target surface.

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

[0007] The present invention provides a high-power wide-angle zoom lens, which includes, from the object side to the image side, a first lens group G1 with positive refractive power, a second lens group G2 with negative refractive power, a third lens group G3 with negative refractive power, a fourth lens group G4 with positive refractive power, a fifth lens group G5 with positive refractive power, and a sixth lens group G6 with negative refractive power;

[0008] The aperture Stop is disposed between the third lens group G3 and the fourth lens group G4;

[0009] The first lens group G1 and the sixth lens group G6 are fixed respectively, and the second lens group G2, the third lens group G3, the fourth lens group G4 and the fifth lens group G5 are moved respectively to achieve zooming from the wide-angle end to the telephoto end.

[0010] Further technology of the present invention:

[0011] Preferably, the first lens group G1 is composed of three negative lenses and one positive lens forming a front group G1a with negative refractive power, two positive and negative cemented lenses forming a middle group G1b with positive refractive power, and a rear group G1c with positive refractive power; when the object moves from infinity to a close distance, the positive refractive power middle group G1b of the first lens group G1 moves from the object side to the image side to achieve focusing, and the conditional expressions (1), (2), (3), (4) and (5) are satisfied;

[0012] 0.6 ≤ | F1 a / F1 |≤1.5 (1)

[0013] 1.5 ≤ |F1 b / Ft | ≤3 (2)

[0014] 0.3 ≤ |WI / F2| ≤0.8 (3)

[0015] 4 ≤ WL / F1 ≤12 (4)

[0016] 2.5 ≤ | F1 a / Fw |≤5 (5)

[0017] in,

[0018] F1a: focal length of the front lens group G1a of the first lens group G1;

[0019] F1 b: focal length of the middle group G1 b of the first lens group G1;

[0020] F1: focal length of the first lens group G1;

[0021] F2: focal length of the first lens group G2;

[0022] Ft: The focal length of the telephoto end of the optical system at infinity;

[0023] Fw: focal length of the entire optical system at the wide-angle end at infinity;

[0024] WL: optical system length, the distance from the first surface on the object side to the image plane;

[0025] WI: The maximum paraxial image height at the wide-angle end at infinity, WI = Fw × tanωw; where ωw is the half field of view at the wide-angle end.

[0026] If the upper limit of conditional expression (1) 0.6≤|F1 a / F1|≤1.5 is exceeded, the refractive power of the middle group G1b of the first lens group G1 is too weak, and it is difficult to achieve the requirement of a field of view greater than 90 degrees. If the requirement of an ultra-wide-angle field of view of 90 degrees is to be achieved, the volume of the first lens group G1 will become very large, and it is difficult to achieve the goal of miniaturization. If the lower limit of conditional expression (1) is exceeded, although the wide-angle field of view can be achieved while achieving 90 degrees, the miniaturization requirement can also be achieved, but because the refractive power of the front group G1a is too strong, it will be difficult to correct aberrations such as spherical aberration, marginal coma, and optical distortion, and it is very difficult to achieve high performance requirements.

[0027] If the upper limit of conditional expression (2) 1.5≤|F1 b / Ft|≤3 is exceeded, the refractive power of the middle group G1b of the first lens group G1 will be very weak, and when focusing at a close distance, the movement of the middle group G1b will be large, making it difficult to achieve the close-range focusing function. If the lower limit of conditional expression (2) is exceeded, the refractive power of the middle group G1b will be very strong, and although the close-range focusing function can be easily achieved, the refractive power of the middle group G1b is too strong, which will make it difficult to correct various aberrations well, making it very difficult to achieve high performance.

[0028] If the upper limit of conditional expression (3) 0.3≤|WI / F2|≤0.8 is exceeded, the refractive power of the second lens group G2 will be very weak. If a zoom ratio of 7 times or more is achieved, the movement amount S2 of the second lens group G2 will become very large, making it very difficult to achieve miniaturization. If the lower limit of conditional expression (3) is exceeded, the refractive power of the second lens group G2 will be very strong. Although it is very advantageous to achieve miniaturization, because the refractive power is too strong, it will be difficult to correct aberrations such as marginal coma, spherical aberration, and optical distortion, making it very difficult to achieve high performance.

[0029] If the upper limit of conditional expression (4) 4≤WL / F1≤12 is exceeded, the refractive power of the first lens group G1 is too strong. Although it is very beneficial for miniaturization design, because the refractive power is too strong, aberrations such as spherical aberration and dispersion are difficult to be well corrected, and it becomes very difficult to achieve high performance. If the lower limit of conditional expression (4) is exceeded, although good aberration correction can be achieved and high performance requirements can be achieved, because the refractive power of the first lens group G1 is too weak, the refractive power of the corresponding second lens group will also become weak. While achieving miniaturization, it is difficult to achieve a zoom ratio of more than 7 times. Therefore, it is difficult to achieve the goal of high-magnification zoom. If a magnification of more than 7 times is achieved, the volume will become very large.

[0030] If the upper limit of conditional expression (5) 2.5≤|F1 a / Fw|≤5 is exceeded, the refractive power of the front group G1a of the first lens group G1 is too weak, and it is difficult to achieve the requirement of a field angle of more than 90 degrees at the wide-angle end; if the lower limit of conditional expression (5) is exceeded, the refractive power of the front group G1a of the first lens group G1 is very strong. Although it is easy to achieve the requirement of a field angle of more than 90 degrees at the wide-angle end, since the refractive power of the first lens group G1a is too strong, it will be difficult to correct aberrations such as edge dispersion, edge coma, and optical distortion, thereby making it very difficult to achieve high performance.

[0031] Preferably, when the third group G3 moves from the wide-angle end to the telephoto end, the moving direction is reversed midway to form a "U"-shaped moving trajectory, and conditional formula (6) is satisfied;

[0032] 5≤(S2+S3+S4+S5) / WI ≤ 8 (6)

[0033] in,

[0034] S2: the total movement of the second lens group G2 when zooming from the wide-angle end to the telephoto end;

[0035] S3: the total movement of the third lens group G3 when zooming from the wide-angle end to the telephoto end;

[0036] S4: the total movement of the fourth lens group G4 when zooming from the wide-angle end to the telephoto end;

[0037] S5: The total movement amount of the fifth lens group G5 when zooming from the wide-angle end to the telephoto end.

[0038] If the upper limit of conditional expression (6) 5≤(S2+S3+S4+S5) / WI≤8 is exceeded, the sum of the movement amounts of each group is too large. Although it is easy to achieve a zoom ratio of more than 7 times, the entire optical system will be bulky and heavy, and its practicality will be poor. If the lower limit of conditional expression (6) is exceeded, although it is easy to achieve the design requirements of miniaturization, it is difficult to achieve a high-magnification zoom ratio of more than 7 times because the movement amount of the moving group is too small.

[0039] Preferably, the sixth lens group G6 is divided into two parts, a front part G6a with negative refractive power and a rear part G6b with positive refractive power, and the rear part G6b is moved to adjust the length of the back focal length BF of the optical system, and the condition (7) is satisfied;

[0040] 2≤F6b / BF ≤ 15 (7)

[0041] in,

[0042] F6b: focal length of the rear portion G6b of the sixth lens group G6.

[0043] If the upper limit of conditional expression (7) 2≤F6b / BF≤15 is exceeded, the refractive power of the rear portion G6b of the sixth lens group is too weak, and if the rear focal length BF is adjusted, the movement amount will become large, and the effect is not obvious. If the lower limit of conditional expression (7) is exceeded, the refractive power of the sixth lens group G6b is too strong, and when the rear focal length BF is adjusted, although the movement amount is small, it is too sensitive, resulting in poor adjustment accuracy. At the same time, because the refractive power of the rear portion G6b is too strong, it is easy to cause performance degradation.

[0044] The invention also provides a digital camera having the high-magnification wide-angle zoom lens.

[0045] The invention also provides a camera having the high-magnification wide-angle zoom lens.

[0046] The beneficial effects of the present invention are:

[0047] The present invention provides a miniaturized, high-performance, low-cost super wide-angle zoom lens with a wide-angle field of view exceeding 90 degrees and a zoom ratio exceeding 7 times, which can be widely used in digital camera lenses, video camera lenses, and especially in the field of broadcast-level zoom lenses for broadcasting. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 is an optical structure diagram of the first embodiment of the present invention;

[0049] Figure 2 The spherical aberration, field curvature aberration, distortion aberration and chromatic aberration of magnification at infinity and the minimum photographic distance of the first embodiment;

[0050] Figure 3 is an optical structure diagram of a second embodiment of the present invention;

[0051] Figure 4 These are the spherical aberration, field curvature, distortion, and lateral chromatic aberration at infinity and at the minimum photographic distance of the second embodiment. DETAILED DESCRIPTION

[0052] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be further described in detail below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention but not all. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0053] First embodiment:

[0054] like Figure 1 As shown, from the object side to the image side, it includes a first lens group G1 with positive refractive power, a second lens group G2 with negative refractive power, a third lens group G3 with negative refractive power, a fourth lens group G4 with positive refractive power, a fifth lens group G5 with positive refractive power, and a sixth lens group G6. The aperture Stop is set between the third lens group G3 and the fourth lens group G4. When zooming from the wide-angle end to the telephoto end, the first lens group G1 and the sixth lens group G6 are fixed, the second lens group G2 moves from the object side to the image side, the movement amount is S2, the third lens group G3 first moves from the image side to the object side, turns back halfway and moves from the object side to the image side, the total movement amount is S3, the fourth lens group G4 and the fifth lens group G5 move from the image side to the object side, and the movement amounts are S4 and S5 respectively, wherein the above-mentioned first lens group G1 consists of three parts, namely, a negative refractive power front group G1a composed of three negative lenses and one positive lens, a middle group G1b composed of two positive and negative cemented lenses, and a positive refractive power rear group G1c; when the object moves from infinity to close distance, the positive refractive power middle group G1b of the above-mentioned first lens group G1 moves from the object side to the image side to achieve focusing. The sixth lens group G6 is divided into two parts, a front part G6a with negative refractive power and a rear part G6b with positive refractive power. When adjusting the length of the back focal length BF (back focus), the rear part G6b of the sixth lens group G6 is moved to achieve fine adjustment of the back focal length BF.

[0055] The spherical aberration, field curvature aberration, distortion aberration and chromatic aberration of magnification at infinity and the closest photographic distance of the first embodiment are as follows: Figure 2 shown.

[0056] The data of the first embodiment are as follows.

[0057] R (mm): The radius of curvature of each surface.

[0058] D(mm): The distance between each lens and the thickness of the lens.

[0059] Nd: The refractive index of each glass at the d line.

[0060] Vd: Abbe number of glass.

[0061] Focal distance: 12.2518~42.8793~97.9636.

[0062] Fno:4.0~4.0~4.0.

[0063] Half picture angle ω: 52.2552~18.6346~8.3603.

[0064]

[0065]

[0066]

[0067]

[0068]

[0069]

[0070] Aspheric shape definition:

[0071] y: radial coordinate from the optical axis.

[0072] z: The offset in the direction of the optical axis starting from the intersection point of the aspherical surface and the optical axis.

[0073] r: The radius of curvature of the reference sphere of the aspheric surface.

[0074] K, 4th, 6th, 8th, 10th, 12th aspheric coefficients

[0075]

[0076] Second embodiment:

[0077] like Figure 3As shown, from the object side to the image side, it includes a first lens group G1 with positive refractive power, a second lens group G2 with negative refractive power, a third lens group G3 with negative refractive power, a fourth lens group G4 with positive refractive power, a fifth lens group G5 with positive refractive power, and a sixth lens group G6. The aperture Stop is set between the third lens group G3 and the fourth lens group G4. When zooming from the wide-angle end to the telephoto end, the first lens group G1 and the sixth lens group G6 are fixed, the second lens group G2 moves from the object side to the image side, the movement amount is S2, the third lens group G3 first moves from the image side to the object side, turns back halfway and moves from the object side to the image side, the total movement amount is S3, the fourth lens group G4 and the fifth lens group G5 move from the image side to the object side, and the movement amounts are S4 and S5 respectively, wherein the above-mentioned first lens group G1 consists of three parts, namely, a negative refractive power front group G1a consisting of three negative lenses and one positive lens, a middle group G1b consisting of two positive and negative cemented lenses, and a positive refractive power rear group G1c; when the object moves from infinity to close distance, the positive refractive power middle group G1b of the above-mentioned first lens group G1 moves from the object side to the image side to achieve focusing. The sixth lens group G6 is divided into two parts, a front part G6a with negative refractive power and a rear part G6b with positive refractive power. When adjusting the length of the back focal length BF (back focus), the rear part G6b of the sixth lens group G6 is moved to achieve fine adjustment of the back focal length BF.

[0078] The spherical aberration, field curvature aberration, distortion aberration and chromatic aberration of magnification at infinity and the closest photographic distance of the second embodiment are as follows: Figure 4 shown.

[0079] The data of the second embodiment are as follows.

[0080] R (mm): The radius of curvature of each surface.

[0081] D(mm): The distance between each lens and the thickness of the lens.

[0082] Nd: The refractive index of each glass at the d line.

[0083] Vd: Abbe number of glass.

[0084] Focus distance: 12.35~43.225~115.9997.

[0085] Fno:4.0~4.0~4.0.

[0086] Half picture angle ω: 52.0722~18.1970~6.9731.

[0087]

[0088]

[0089]

[0090]

[0091]

[0092]

[0093] Aspheric shape definition:

[0094] y: radial coordinate from the optical axis.

[0095] z: The offset in the direction of the optical axis starting from the intersection point of the aspherical surface and the optical axis.

[0096] r: The radius of curvature of the reference sphere of the aspheric surface.

[0097] K, 4th, 6th, 8th, 10th, 12th aspheric coefficients

[0098]

[0099] Conditional summary table:

[0100]

[0101] The above contents are merely examples and explanations of the structure of the present invention. The technicians in this technical field may make various modifications or additions to the specific embodiments described 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 protection scope of the present invention.

Claims

1. High magnification wide-angle zoom lens, It is characterized in that The lens system includes, from the object side to the image side, a first lens group G1 with positive refractive power, a second lens group G2 with negative refractive power, a third lens group G3 with negative refractive power, a fourth lens group G4 with positive refractive power, a fifth lens group G5 with positive refractive power, and a sixth lens group G6 with negative refractive power; The aperture Stop is disposed between the third lens group G3 and the fourth lens group G4; The first lens group G1 and the sixth lens group G6 are fixed respectively, and the second lens group G2, the third lens group G3, the fourth lens group G4 and the fifth lens group G5 are moved respectively to achieve zooming from the wide-angle end to the telephoto end.

2. The high-power wide-angle zoom lens according to claim 1, It is characterized in that The first lens group G1 is composed of three negative lenses and one positive lens forming a front group G1a with negative refractive power, two positive and negative cemented lenses forming a middle group G1b with positive refractive power, and a rear group G1c with positive refractive power; when the object moves from infinity to a close distance, the positive middle group G1b of the first lens group G1 moves from the object side to the image side to achieve focusing, and the conditional expressions (1), (2), (3), (4) and (5) are satisfied; 0.6 ≤ | F1 a / F1 |≤1.5 (1) 1.5 ≤ |F1 b / Ft | ≤3 (2) 0.3 ≤ |WI / F2| ≤0.8 (3) 4 ≤ WL / F1 ≤12 (4) 2.5 ≤ | F1 a / Fw |≤5 (5) in, F1a: focal length of the front lens group G1a of the first lens group G1; F1 b: focal length of the middle group G1 b of the first lens group G1; F1: focal length of the first lens group G1; F2: focal length of the first lens group G2; Ft: The focal length of the telephoto end of the optical system at infinity; Fw: focal length of the entire optical system at the wide-angle end at infinity; WL: optical system length, the distance from the first surface on the object side to the image plane; WI: The maximum paraxial image height at the wide-angle end at infinity, WI = Fw × tanωw; where ωw is the half field of view at the wide-angle end.

3. The high-power wide-angle zoom lens according to claim 2, It is characterized in that When the third group G3 moves from the wide-angle end to the telephoto end, the moving direction will be reversed in the middle, forming a "U"-shaped moving trajectory, and satisfying conditional formula (6); 5≤(S2+S3+S4+S5) / WI ≤ 8 (6) in, S2: the total movement of the second lens group G2 when zooming from the wide-angle end to the telephoto end; S3: the total movement of the third lens group G3 when zooming from the wide-angle end to the telephoto end; S4: the total movement of the fourth lens group G4 when zooming from the wide-angle end to the telephoto end; S5: The total movement amount of the fifth lens group G5 when zooming from the wide-angle end to the telephoto end.

4. The high-power wide-angle zoom lens according to claim 1, It is characterized in that The sixth lens group G6 is divided into two parts, a front part G6a with negative refractive power and a rear part G6b with positive refractive power, and the rear part G6b is moved to adjust the length of the back focal length BF of the optical system, and the conditional formula (7) is satisfied; 2≤F6b / BF ≤ 15 (7) in, F6b: focal length of the rear portion G6b of the sixth lens group G6.

5. A digital camera having the high-magnification wide-angle zoom lens according to any one of claims 1 to 4.

6. A camera having the high-magnification wide-angle zoom lens according to any one of claims 1 to 4.

Images