A F-mount large-surface continuous zoom lens

Abstract

The invention discloses an F-mount large-target-surface continuous zoom lens, wherein the continuous zoom lens is provided with a front fixed group A with negative focal power, a zoom group B with positive focal power, an aperture stop C, a compensation group D with positive focal power, and a rear fixed group E with negative focal power in sequence from the object plane to the image plane; the front fixed group A comprises a first cemented group in which a biconvex lens A1 and a biconcave lens A2 are closely connected; the zoom group B comprises a second cemented group in which a biconcave lens B1 and a biconvex lens B2 are closely connected, and a third cemented group in which a biconvex lens B3 and a negative meniscus lens B4 are closely connected; the compensation group D comprises a fourth cemented group in which a negative meniscus lens D1 and a biconvex lens D2 are closely connected; and the rear fixed group E comprises a fifth cemented group in which a plano-concave lens E1, a biconvex lens E2, and a biconcave lens E3 are closely connected. The F-mount large-target-surface continuous zoom lens provided by the invention can be used in conjunction with image sensors of 1.75 inches or less.

Description

Technical Field

[0001] The invention belongs to the technical field of optical lenses, and in particular relates to an F-interface large-target-surface continuous zoom lens. Background Art

[0002] A continuously zoom lens is a lens whose magnification is continuously adjustable within a certain range. With the continuous development of machine vision and industrial automation, continuously zoom lenses have been used more and more widely.

[0003] There are two types of continuous zoom lenses on the market:

[0004] 1. Continuously variable magnification lens with constant working distance. The mainstream zoom range of this type of lens is 0.7-4.5x, and the image plane of the matching image sensor is mostly less than 1 / 2 inch, with a small field of view; because the working distance is fixed, there is no need to repeatedly adjust the object distance during observation, which is more convenient to use, but it is less versatile for objects with large height differences. For example, a Chinese patent with publication number CN110208933A discloses a large zoom ratio, high resolution, large field of view, continuous zoom lens, comprising a front fixed objective lens, a front fixed optical component, a high-power diaphragm, a zoom optical component, a low-power diaphragm, a compensating optical component and a rear fixed optical component, which are arranged in sequence along the optical axis from the object side to the image side. The focal length of the front fixed objective lens and the focal length of the front fixed optical component are both positive, the focal length of the zoom optical component is negative and moves along the optical axis relative to the front fixed optical component, the focal length of the compensating optical component is positive and moves along the optical axis relative to the rear fixed optical component, and the focal length of the rear fixed optical component is negative; the high-power diaphragm is arranged on the front fixed optical component and is fixed, and the low-power diaphragm is arranged on the compensating optical component and moves synchronously with the compensating optical component.

[0005] 2. Continuously variable magnification lens with changing working distance. This type of lens is often used for macro observation. The image plane of the matching image sensor can reach 1 inch, but there is almost no continuously variable magnification lens on the market that can match the 1.75-inch image sensor. For example, the Chinese patent document with publication number CN203658655U discloses a 50x high-definition variable magnification lens, which includes a front fixed group, a variable magnification group, a compensation group and a rear fixed group from front to back along the optical axis. The front fixed group includes a front protective glass, a negative positive double cemented lens group and a negative positive double cemented lens group; the variable magnification group includes a positive negative positive triple cemented lens group and a single double concave negative lens; the compensation group includes a plano-concave negative lens, a plano-convex positive lens and a positive negative double cemented lens group; the rear fixed group includes a plano-concave negative lens, a convex-concave negative lens and a double convex positive lens, and all the above lenses share a common optical axis. The variable magnification group and the compensation group move left and right along the optical axis to continuously change the focal length of the lens within the range of 15mm to 750mm to achieve zooming.

[0006] At the same time, most of the continuous zoom lenses on the market can only match C-mount or CS-mount industrial cameras, and few lenses can match F-mount industrial cameras. Therefore, it is urgent to develop a continuous zoom lens that can match F-mount industrial cameras and 1.75-inch large-image sensor to fill the market gap. Summary of the invention

[0007] In view of the problem that existing continuously zooming lenses are compatible with smaller target surfaces, the present invention provides an F-mount continuously zooming lens with a large target surface, so as to achieve the purpose of being able to adapt to image sensors smaller than 1.75 inches.

[0008] The technical solution of the present invention is:

[0009] The invention discloses an F-mount large-target-surface continuous zoom lens, which comprises, from the object plane to the image plane, a front fixed group A with negative optical power, a zoom group B with positive optical power, an aperture stop C, a compensation group D with positive optical power, and a rear fixed group E with negative optical power. The front fixed group A comprises a first cemented group in which a biconvex lens A1 and a biconcave lens A2 are closely connected. The zoom group B comprises a second cemented group in which a biconcave lens B1 and a biconvex lens B2 are closely connected, and a third cemented group in which a biconvex lens B3 and a negative meniscus lens B4 are closely connected. The compensation group D comprises a fourth cemented group in which a negative meniscus lens D1 and a biconvex lens D2 are closely connected. The rear fixed group E comprises a fifth cemented group in which a plano-concave lens E1, a biconvex lens E2 and a biconcave lens E3 are closely connected.

[0010] Furthermore, the positions of the fixed group and the image sensor of the zoom lens are fixed, and the positions of the zoom group and the compensation group are adjustable; when the zoom lens zooms from a low magnification to a high magnification, the zoom group B approaches the fixed group A, and the compensation group D approaches the aperture stop C. During the zoom process, the position of the aperture stop C is fixed, and the aperture remains unchanged.

[0011] Furthermore, the focal lengths of the front fixed group A, the zoom group B, the compensation group D, and the rear fixed group E respectively satisfy the following conditional formula with the focal length of the continuous zoom lens:

[0012] 10.0<|f1 / f|<100.0;

[0013] 0.5<|f2 / f|<5.0;

[0014] 0.6<|f3 / f|<6.0;

[0015] 1.0<|f4 / f|<10.0;

[0016] Among them, f is the total focal length of the continuous zoom lens when the magnification is 0.25x, f1 is the focal length of the front fixed group A, f2 is the focal length of the zoom group B, f3 is the focal length of the compensation group D, and f4 is the focal length of the rear fixed group E.

[0017] Further preferably, the focal lengths of the front fixed group A, the zoom group B, the compensation group D, and the rear fixed group E respectively satisfy the following conditional formula with the focal length of the continuous zoom lens:

[0018] 17.4<|f1 / f|<46.0;

[0019] 1.1<|f2 / f|<1.4;

[0020] 1.2<|f3 / f|<1.4;

[0021] 1.7<|f4 / f|<2.7;

[0022] Wherein, f is the total focal length of the zoom lens when the magnification is 0.25x, f1 is the focal length of the front fixed group A, f2 is the focal length of the zoom group B, f3 is the focal length of the compensation group D, and f4 is the focal length of the rear fixed group E. Within this range, the MTF curve of the zoom lens is closer to the diffraction limit, and the spot diagram size is smaller.

[0023] Furthermore, the focal length, curvature radius and refractive index of the lens of the continuous zoom lens meet the following conditions:

[0024] A1 50＜f1＜150 150＜R1＜450 -200＜R2＜-100 1.6＜n1＜1.9 A2 -150＜f2＜-50 -200＜R3＜-100 50＜R4＜120 1.4＜n2＜1.6 B1 -30＜f3＜-10 -50＜R5＜-10 15＜R6＜1000 1.7＜n3＜2 B2 10＜f4＜30 15＜R7＜1000 -50＜R8＜-20 1.8＜n4＜2 B3 15＜f5＜45 50＜R9＜100 -50＜R10＜-10 1.6＜n5＜1.8 B4 -60＜f6＜-20 -50＜R11＜-10 -200＜R12＜-100 1.8＜n6＜2 D1 -60＜f7＜-20 50＜R13＜100 10＜R14＜40 1.7＜n7＜2 D2 15＜f8＜45 10＜R15＜40 -300＜R16＜-100 1.6＜n8＜1.8 E1 -60＜f9＜-20 R17>100 / R17<-100 10＜R18＜40 1.5＜n9＜1.7 E2 10＜f10＜30 20＜R19＜50 -30＜R20＜-10 1.8＜n10＜2 E3 -30＜f11＜-10 -30＜R21＜-10 50＜R22＜150 1.7＜n11＜1.9

[0025] Among them, "f" is the focal length, "n" is the refractive index, "R" is the curvature radius, and the "-" sign indicates that the direction is negative; f1 to f11 correspond to the focal lengths of A1 to E3 respectively; n1 to n11 correspond to the refractive indices of A1 to E3 respectively; R1, R3, R5, R7, R9, R11, R13, R15, R17, R19, R21 correspond to the curvature radii of the surfaces of A1 to E3 close to the object side respectively, and R2, R4, R6, R8, R10, R12, R14, R16, R18, R20, R22 correspond to the curvature radii of the surfaces of A1 to E3 away from the object side respectively.

[0026] Further preferably, the focal length, curvature radius and refractive index of the lens of the continuous zoom lens meet the following conditions:

[0027]

[0028]

[0029] Among them, "f" is the focal length, "n" is the refractive index, "R" is the curvature radius, and the "-" sign indicates that the direction is negative; f1 to f11 correspond to the focal lengths of A1 to E3 respectively; n1 to n11 correspond to the refractive indices of A1 to E3 respectively; R1, R3, R5, R7, R9, R11, R13, R15, R17, R19, R21 correspond to the curvature radii of the surfaces of A1 to E3 close to the object side respectively, and R2, R4, R6, R8, R10, R12, R14, R16, R18, R20, R22 correspond to the curvature radii of the surfaces of A1 to E3 away from the object side respectively.

[0030] Furthermore, the focal length range of the continuous zoom lens is 55-70 mm, and the working distance is 80-260 mm.

[0031] Furthermore, the continuous zoom lens can achieve 0.25-1x continuous zoom, match a 1.75-inch image sensor, have an optical back focus greater than 40mm, and can match an F-mount industrial camera.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] The F-mount large-target-surface continuous zoom lens provided by the present invention adopts a four-group structure, and achieves a zoom range of 0.25 to 1x by moving the zoom group and the compensation group; each group uses less than 4 lenses, and can achieve better imaging quality and a larger target surface with a smaller number of lenses, and can be used with image sensors below 1.75 inches. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 Schematic diagram of the imaging system of the continuously variable magnification lens in Example 1 when the magnification is 0.25-1x;

[0035] Figure 2 This is the MTF curve diagram when the magnification of the zoom lens in Example 1 is 0.25x;

[0036] Figure 3 This is the MTF curve diagram when the magnification of the zoom lens in Example 1 is 0.5x;

[0037] Figure 4 This is the MTF curve diagram when the magnification of the zoom lens in Example 1 is 0.75x;

[0038] Figure 5 This is the MTF curve diagram of the continuously zooming lens in Example 1 when the magnification is 1x;

[0039] Figure 6 This is the spot diagram when the magnification of the zoom lens in Example 1 is 0.25x;

[0040] Figure 7 This is the spot diagram when the magnification of the zoom lens in Example 1 is 0.5x;

[0041] Figure 8 This is the spot diagram when the magnification of the zoom lens in Example 1 is 0.75x;

[0042] Fig. 9 This is the point diagram when the magnification of the continuous zoom lens in Example 1 is 1x.

[0043] Fig.10 Schematic diagram of the imaging system of the continuously variable magnification lens in Example 2 when the magnification is 0.25-1x;

[0044] Fig.11 This is the MTF curve diagram when the magnification of the zoom lens in Example 2 is 0.25x;

[0045] Fig.12 This is the MTF curve diagram when the magnification of the zoom lens in Example 2 is 0.5x;

[0046] Fig.13 This is the MTF curve diagram when the magnification of the zoom lens in Example 2 is 0.75x;

[0047] Fig.14 This is the MTF curve diagram of the continuously zooming lens in Example 2 when the magnification is 1x;

[0048] Fig.15 This is the spot diagram when the magnification of the zoom lens in Example 2 is 0.25x;

[0049] Fig.16 This is the spot diagram when the magnification of the zoom lens in Example 2 is 0.5x;

[0050] Fig.17 This is the spot diagram when the magnification of the zoom lens in Example 2 is 0.75x;

[0051] Fig.18 This is the point diagram when the magnification of the continuous zoom lens in Example 2 is 1x.

[0052] Fig.19 Schematic diagram of the imaging system of the continuously variable magnification lens in Example 3 when the magnification is 0.25-1x;

[0053] Fig. 20 This is the MTF curve diagram when the magnification of the zoom lens in Example 3 is 0.25x;

[0054] Fig.21 This is the MTF curve diagram when the magnification of the zoom lens in Example 3 is 0.5x;

[0055] Fig. 22 This is the MTF curve diagram when the magnification of the zoom lens in Example 3 is 0.75x;

[0056] Fig.23 This is the MTF curve diagram of the continuously zooming lens in Example 3 when the magnification is 1x;

[0057] Fig.24 This is the spot diagram when the magnification of the zoom lens in Example 3 is 0.25x;

[0058] Fig.25 This is the spot diagram when the magnification of the zoom lens in Example 3 is 0.5x;

[0059] Fig.26 This is the spot diagram when the magnification of the zoom lens in Example 3 is 0.75x;

[0060] Fig. 27 This is the point diagram when the magnification of the continuous zoom lens in Example 3 is 1x. DETAILED DESCRIPTION

[0061] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0062] like Figure 1 As shown, an F-mount large-target-surface continuous zoom lens includes, from the object plane to the image plane, a front fixed group A with negative optical power, a zoom group B with positive optical power, an aperture stop C, a compensation group D with positive optical power, and a rear fixed group E with negative optical power. The front fixed group A includes a first cemented group of a biconvex lens A1 and a biconcave lens A2 in close contact; the zoom group B includes a second cemented group of a biconcave lens B1 and a biconvex lens B2 in close contact, and a third cemented group of a biconvex lens B3 and a negative meniscus lens B4 in close contact; the compensation group D includes a fourth cemented group of a negative meniscus lens D1 and a biconvex lens D2 in close contact; and the rear fixed group E includes a fifth cemented group of a plano-concave lens E1, a biconvex lens E2, and a biconcave lens E3 in close contact. Among them, the positions of the fixed group and the image sensor of the continuous zoom lens are fixed, and the positions of the zoom group and the compensation group are adjustable. When the zoom lens changes from low magnification to high magnification, the zoom group B moves closer to the fixed group A, and the compensation group D moves closer to the aperture stop C. During the zoom process, the position of the aperture stop C is fixed, and the diameter remains unchanged.

[0063] Example 1

[0064] like Figure 1 As shown, in this embodiment, various parameters of the lens of the continuous zoom lens are shown in Table 1.

[0065] Table 1 Lens parameters of the continuous zoom lens in Example 1

[0066]

[0067]

[0068] When the magnification is 0.25x, the focal length of the continuous zoom lens is 68.5 mm, and when the magnification is 1x, the focal length of the continuous zoom lens is 61.4 mm.

[0069] Here we take the low magnification of 0.25x, the medium magnification of 0.5x, the high magnification of 0.75x, and the maximum magnification of 1x as examples to analyze the aberration.

[0070] The MTF curves at different magnifications are as follows: Figures 2 to 5 As shown in Figure 1, overall, the MTF curves for all magnifications are relatively smooth. Figure 2 As shown in the figure, when the magnification is 0.25x, the MTF of the zoom lens is basically greater than 0.3 at 140lp / mm. Figure 3 As shown in the figure, when the magnification is 0.5x, the MTF of the zoom lens is basically greater than 0.3 at 140lp / mm. Figure 4 As shown in the figure, the MTF of the zoom lens is greater than 0.2 at 140lp / mm when the magnification is 0.75x. Figure 5 As shown, when the magnification is 1x, the MTF of the continuous zoom lens is basically greater than 0.2 at 140lp / mm.

[0071] The spot diagrams at different magnifications are shown below. Figures 6 to 9 As shown, Figure 6 This is the spot diagram at a magnification of 0.25x. Figure 7 This is the spot diagram when the magnification is 0.5x. Figure 8 This is the spot diagram at a magnification of 0.75x. Fig. 9 This is the spot diagram at a magnification of 1x. The spot diagram of the zoom lens at magnifications of 0.25x and 0.5x is better than that at magnifications of 0.75x and 1x. Overall, the spot diagram size is small, and the RMS diameter is basically controlled within 7.2μm, which meets the resolution requirements of the image sensor.

[0072] Example 2

[0073] like Fig.10 As shown, in this embodiment, various parameters of the lens of the continuous zoom lens are shown in Table 2.

[0074] Table 2 Lens parameters of the continuous zoom lens in Example 2

[0075]

[0076]

[0077] When the magnification is 0.25x, the focal length of the continuous zoom lens is 66.1 mm, and when the magnification is 1x, the focal length of the continuous zoom lens is 58.2 mm.

[0078] Here we take the low magnification of 0.25x, the medium magnification of 0.5x, the high magnification of 0.75x, and the maximum magnification of 1x as examples to analyze the aberration.

[0079] The MTF curves at different magnifications are as follows: Figures 11 to 14 As shown in Figure 1, overall, the MTF curves for all magnifications are relatively smooth. Fig.11 As shown in the figure, when the magnification is 0.25x, the MTF of the zoom lens is basically greater than 0.15 at 140lp / mm. Fig.12 As shown in the figure, when the magnification is 0.5x, the MTF of the zoom lens is basically greater than 0.2 at 140lp / mm. Fig.13 As shown in the figure, when the magnification is 0.75x, the MTF of the zoom lens is basically greater than 0.2 at 140lp / mm. Fig.14 As shown, when the magnification is 1x, the MTF of the continuous zoom lens is basically greater than 0.1 at 140lp / mm.

[0080] The spot diagrams at different magnifications are shown below. Figures 15 to 18 As shown, Fig.15 This is the spot diagram at a magnification of 0.25x. Fig.16 This is the spot diagram when the magnification is 0.5x. Fig.17 This is the spot diagram at a magnification of 0.75x. Fig.18 This is the spot diagram at a magnification of 1x.

[0081] Example 3

[0082] like Fig.19 As shown, in this embodiment, various parameters of the lens of the continuous zoom lens are shown in Table 3.

[0083] Table 3 Lens parameters of the continuous zoom lens in Example 3

[0084]

[0085]

[0086] When the magnification is 0.25x, the focal length of the continuous zoom lens is 66.5 mm, and when the magnification is 1x, the focal length of the continuous zoom lens is 58.1 mm.

[0087] Here we take the low magnification of 0.25x, the medium magnification of 0.5x, the high magnification of 0.75x, and the maximum magnification of 1x as examples to analyze the aberration.

[0088] The MTF curves at different magnifications are as follows: Figures 20-23 As shown in Figure 1, overall, the MTF curves for all magnifications are relatively smooth. Fig. 20 As shown in the figure, when the magnification is 0.25x, the MTF of the zoom lens is basically greater than 0.25 at 140lp / mm. Fig.21 As shown in the figure, when the magnification is 0.5x, the MTF of the zoom lens is basically greater than 0.2 at 140lp / mm. Fig. 22 As shown in the figure, when the magnification is 0.75x, the MTF of the zoom lens is basically greater than 0.2 at 140lp / mm. Fig.23 As shown, when the magnification is 1x, the MTF of the continuous zoom lens is basically greater than 0.1 at 140lp / mm.

[0089] The spot diagrams at different magnifications are shown below. Figures 24-27 As shown, Fig.24 This is the spot diagram at a magnification of 0.25x. Fig.25 This is the spot diagram when the magnification is 0.5x. Fig.26 This is the spot diagram at a magnification of 0.75x. Fig. 27 This is the spot diagram at a magnification of 1x.

[0090] The embodiments described above provide a detailed description of the technical solutions and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, supplements and equivalent substitutions made within the scope of the principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An F-mount large-surface continuous zoom lens, characterized in that: The continuously variable power lens is composed of a front fixed group A with negative optical focal length, a variable power group B with positive optical focal length, an aperture stop C, a compensation group D with positive optical focal length, and a rear fixed group E with negative optical focal length, which are arranged in sequence from the object plane to the image plane; the front fixed group A is composed of a first cemented group in which a biconvex lens A1 and a biconcave lens A2 are in close contact; the variable power group B is composed of a second cemented group in which a biconcave lens B1 and a biconvex lens B2 are in close contact, and a third cemented group in which a biconvex lens B3 and a negative meniscus lens B4 are in close contact; the compensation group D is composed of a fourth cemented group in which a negative meniscus lens D1 and a biconvex lens D2 are in close contact; and the rear fixed group E is composed of a fifth cemented group in which a plano-concave lens E1, a biconvex lens E2, and a biconcave lens E3 are in close contact.

2. The F-mount large-target-area continuous zoom lens according to claim 1, characterized in that: The positions of the fixed group, aperture diaphragm and image sensor are fixed, and the positions of the zoom group and compensation group are adjustable; when the continuous zoom lens changes magnification from low magnification to high magnification, the zoom group B approaches the fixed group A, and the compensation group D approaches the aperture diaphragm C, and the aperture of the aperture diaphragm C remains unchanged during the zoom process.

3. The F-mount large-target-area continuous zoom lens according to claim 1, characterized in that: The focal lengths of the front fixed group A, the zoom group B, the compensation group D, and the rear fixed group E respectively satisfy the following conditional formula with the focal length of the continuous zoom lens: 10.0<|f1 / f|<100.0; 0.5<|f2 / f|<5.0; 0.6<|f3 / f|<6.0; 1.0<|f4 / f|<10.0; Among them, f is the total focal length of the continuous zoom lens when the magnification is 0.25x, f1 is the focal length of the front fixed group A, f2 is the focal length of the zoom group B, f3 is the focal length of the compensation group D, and f4 is the focal length of the rear fixed group E.

4. The F-mount large-surface continuous zoom lens according to claim 1, characterized in that: The focal lengths of the front fixed group A, the zoom group B, the compensation group D, and the rear fixed group E respectively satisfy the following conditional formula with the focal length of the continuous zoom lens: 17.4<|f1 / f|<46.0; 1.1<|f2 / f|<1.4; 1.2<|f3 / f|<1.4; 1.7<|f4 / f|<2.7; Among them, f is the total focal length of the continuous zoom lens when the magnification is 0.25x, f1 is the focal length of the front fixed group A, f2 is the focal length of the zoom group B, f3 is the focal length of the compensation group D, and f4 is the focal length of the rear fixed group E.

5. The F-mount large-target-area continuous zoom lens according to any one of claims 1 to 4, characterized in that: The focal length, curvature radius and refractive index of the zoom lens meet the following conditions: Wherein, "f" is the focal length, "n" is the refractive index, "R" is the curvature radius, and the "-" sign indicates a negative direction; f1 to f11 correspond to the focal lengths of A1 to E3 respectively; n1 to n11 correspond to the refractive indices of A1 to E3 respectively; R1, R3, R5, R7, R9, R11, R13, R15, R17, R19, and R21 correspond to the curvature radii of a surface of A1 to E3 close to the object side, and R2, R4, R6, R8, R10, R12, R14, R16, R18, R20, and R22 correspond to the curvature radii of a surface of A1 to E3 away from the object side.

6. The F-mount large-target-area continuous zoom lens according to any one of claims 1 to 4, characterized in that: The focal length, curvature radius and refractive index of the zoom lens meet the following conditions: Wherein, "f" is the focal length, "n" is the refractive index, "R" is the curvature radius, and the "-" sign indicates a negative direction; f1 to f11 correspond to the focal lengths of A1 to E3 respectively; n1 to n11 correspond to the refractive indices of A1 to E3 respectively; R1, R3, R5, R7, R9, R11, R13, R15, R17, R19, and R21 correspond to the curvature radii of a surface of A1 to E3 close to the object side, and R2, R4, R6, R8, R10, R12, R14, R16, R18, R20, and R22 correspond to the curvature radii of a surface of A1 to E3 away from the object side.

7. The F-mount large-target-area continuous zoom lens according to claim 1, characterized in that: The magnification of the continuous zoom lens is 0.25-1x.

8. The F-mount large-surface continuous zoom lens according to claim 1, characterized in that: The focal length range of the continuous zoom lens is 55-70 mm, and the working distance is 80-260 mm.

9. The F-mount large-surface continuous zoom lens according to claim 1, characterized in that: The optical back focus of the continuous zoom lens is greater than 40 mm and can be matched with an F-mount industrial camera.

Images