Tilt-shift macro lens

Abstract

The utility model discloses a tilt-shift macro lens, which relates to the field of lenses of full-frame digital exchange cameras and structurally comprises a first lens group G1 with negative diopter, a second lens group G2 with positive diopter and a third lens group G3 with negative diopter in sequence from an object side to an image surface side. The aperture Stop is arranged between the second lens group G2 and the third lens group G3; the first lens group G1 is fixed, the second lens group G2 serves as a main focusing lens group and moves from the image plane side to the object side, and the third lens group G3 serves as an auxiliary focusing group to correct aberration caused by movement of the second lens group G2. And the front part of the first lens group G1 is composed of G1a with negative diopter. Under the condition that the size is controlled, the maximum field angle exceeds 45 degrees, the image field is large enough and reaches 65 mm or above, the diameter of the image field exceeds 20 mm of the image field of a full-frame camera, mutual translation of the lens and the camera can be achieved by + / -10 mm or above, tilt shift of the lens and the camera can be achieved by + / -8 degrees or above, and black edge shielding caused by insufficient image fields is avoided.

Description

Technical Field

[0001] The utility model relates to a shift macro lens, which is applied in the lens field of full-frame digital exchange cameras. Background Art

[0002] At present, the known cameras use macro lenses that can form good images from infinity to close distances, and the maximum photographic magnification at the closest distance is 1x (equal magnification). For example, in the known Japanese patent JP 2013-104994, when an object moves from infinity to close distance, the first and fourth lens groups are fixed, and the second and third lens groups move towards each other to achieve focusing. Although good imaging can be achieved, the field of view is very small. However, when used for a full-frame camera to achieve a translation of more than 10 mm, or a tilt shift of more than 8°, the image field diameter is not large enough, and there will be a problem of incomplete coverage. If it is enlarged proportionally, the performance will decrease, and the volume is too large to be usable. There is also the well-known Japanese patent No. JP 2024-29669. The first and fourth lens groups are fixed, and the second and third lens groups move toward each other to achieve focus. Although good imaging can be achieved, the field of view is less than 45°. However, it is used for full-frame cameras to achieve a translation of more than ±10mm, or a tilt shift of more than ±8°. Because the image plane diameter is not large enough, a black edge phenomenon occurs, and the last lens is too close to the image plane. When the translation and tilt movement are realized, there is no space for the mechanical structure to realize it, and interference and other problems are bound to occur. Utility Model Content

[0003] In order to overcome the problem that the above-mentioned known macro lenses cannot achieve a viewing angle of more than 45° on a full-frame body, and can achieve a large range of translation of more than ±10mm and a tilt and shift function of more than ±8°, the utility model will provide a large screen with a photographic magnification from infinity to about 1.0 times, an imaging circle diameter of more than 65mm, and a long back focal length. It can achieve a translation of more than ±10mm and a tilt shift of more than ±8° on a full-frame camera with an image plane diameter of 43.2mm, and a field angle greater than 45° with good imaging.

[0004] In order to achieve the above-mentioned utility model purpose, the utility model adopts the following technical solutions:

[0005] The utility model provides a shift macro lens, which comprises, from the object side to the image side, a first lens group G1 with negative refractive power, a second lens group G2 with positive refractive power, and a third lens group G3 with negative refractive power;

[0006] The aperture Stop is disposed between the second lens group G2 and the third lens group G3;

[0007] The first lens group G1 is fixed, the second lens group G2 is used as a main focus lens group, and moves from the image side to the object side, and the third lens group G3 is used as an auxiliary focus group to correct the aberration caused by the movement of the second lens group G2;

[0008] The front part of the first lens group G1 is composed of negative refractive power G1a, whose focal length is F1a, and satisfies the following conditions (1) and (2):

[0009] 0.6≤|F1a / F0|≤1.0 (1)

[0010] 0.5≤F2 / F0≤1.2 (2)

[0011] in,

[0012] F1a: focal length of the front part G1a of the first lens group;

[0013] F0: focal length of the entire optical system at infinity;

[0014] F2: focal length of the second lens group G2.

[0015] If the upper limit of the conditional expression 0.6≤|F1a / F0|≤1.0(1) is exceeded, the negative refractive power of the front part G1a of the first lens group is relatively weak. If the maximum field of view exceeds 45°, the volume of the first lens group will become very large. Although the performance is easy to achieve, the miniaturization design is more difficult. If the lower limit of the conditional expression (1) is exceeded, although the miniaturization can be achieved while achieving a 45° field of view, the negative refractive power of the first lens group G1 and the positive second lens group G2 cancel each other out, resulting in a very short focal length, making it difficult to achieve equal-magnification macro performance, especially the image curvature in the macro state.

[0016] If the upper limit of the conditional expression 0.5≤F2 / F0≤1.2(2) is exceeded, the refractive power of the positive refractive power second lens group G2 will be too weak. If a 1x macro effect is achieved, the movement of the second lens group G2 will be very large, resulting in the inability to miniaturize. If the lower limit of the conditional expression (2) is exceeded, the refractive power of the positive refractive power second lens group G2 is too strong. Although miniaturization can be easily achieved, the aberration caused by the second lens group G2 is difficult to correct, and it is difficult to achieve high performance requirements.

[0017] Further technology of the utility model:

[0018] Preferably, the setting position of the aperture Stop and the length of the back focus satisfy conditional expressions (3) and (4);

[0019] 0.3≤LS / Ymax≤1.0 (3)

[0020] 0.6≤|F0 / BF_I NF|≤1.6 (4)

[0021] in,

[0022] LS: The distance from the aperture stop to the rearmost surface of the image plane of the optical system at infinity;

[0023] BF_INF: back focal length of the optical system at infinity;

[0024] Ymax: the maximum paraxial image height at infinity; Ymax = F0 × tanω;

[0025] ω: half field of view angle at infinity.

[0026] If the upper limit of the conditional expression 0.3≤LS / Ymax≤1.0(3) is exceeded, the distance from the aperture to the rear face of the optical system is too far, which will cause the outer diameter of the third lens group G3 to be too large, resulting in interference between the shift mechanism and the camera, making it difficult to achieve the pan and tilt shift functions. If the lower limit of the conditional expression (3) is exceeded, the distance from the aperture to the rear face of the optical system is too close. Although the exit pupil is very close and the volume of the third lens group G3 is small, the entrance pupil distance is very far, which will cause the outer diameter of the first lens group G1 to become large, resulting in the volume of the entire optical system becoming very large.

[0027] If the upper limit of the conditional expression 0.6≤|F0 / BF_I NF|≤1.6(4) is exceeded, the back focal length will be very small, that is, the distance between the last surface of the lens and the image plane is too close, which makes it difficult to implement the pan and tilt shift mechanism, resulting in interference with the camera body. If the lower limit of the conditional expression (4) is exceeded, the back focal length will be very large, that is, the distance between the last surface of the optical system and the image plane is too large. Although the pan and tilt shift mechanism is easy to design, the entire optical system will become very large, making miniaturization impossible, high cost, and inapplicable.

[0028] Preferably, the interval between the first lens group G1 and the second lens group G2 in the infinite state satisfies conditional formula (5);

[0029] 0.4≤|D12 / F0|≤1.2 (5)

[0030] in,

[0031] D12: The distance between the first lens group G1 and the second lens group G2 at infinity.

[0032] If the upper limit of the conditional expression 0.4≤|D12 / F0|≤1.2(5) is exceeded, the interval between the first lens group G1 and the second lens group G2 at infinity is large enough, and when focusing, the second lens group G2 has sufficient space to move, and it is easy to achieve a macro effect of equal magnification. However, because the interval is too large, the entire optical system may become huge, the manufacturing cost is too high, and the volume is too large to be applicable. If the lower limit of the conditional expression (5) is exceeded, the focus movement space of the main focus group G2 is very small, and the diopter strength must be increased, which will cause the aberration to deteriorate sharply due to the diopter being too strong, and it is difficult to achieve the effect of 1x macro and high performance.

[0033] Preferably, the movement amounts of the second lens group G2 and the third lens group G3 satisfy conditional expressions (6) and (7);

[0034] 1.0≤|S2_A / S3_A|≤1.7 (6)

[0035] 0.8≤|S2_B / S3_B|≤1.6 (7)

[0036] in,

[0037] S2_A: the focus movement amount of the second lens group G2 when the photographic distance is from infinity to the photographic magnification of 0.5 times;

[0038] S3_A: the focus movement amount of the third lens group G3 when the photographic distance is from infinity to the photographic magnification of 0.5 times;

[0039] S2_B: the focus movement amount of the second lens group G2 when the photographic distance is from infinity to the photographic magnification of 1.0 times;

[0040] S3_B: The focus movement amount of the third lens group G3 when the photographic distance is from infinity to the photographic magnification of 1.0.

[0041] If the upper limit of the conditional expression 1.0≤|S2_A / S3_A|≤1.7(6) is exceeded, the movement of the second lens group G2 of the main focus group is too large, and the spherical aberration and image curvature generated during the focusing process are insufficiently corrected by the third lens group G3 of the auxiliary focus group, resulting in a decrease in performance around 0.5 times, especially the image curvature is difficult to correct. If the lower limit of the conditional expression (6) is exceeded, although the third lens group G3 of the auxiliary focus group provides sufficient aberration correction, it will offset the movement effect of the second lens group G2 of the main focus group, and the focusing movement will increase, causing the entire optical system to become very large, making miniaturization very difficult.

[0042] If the upper limit of the conditional expression 0.8≤|S2_B / S3_B|≤1.6(7) is exceeded, the movement of the second lens group G2 of the main focus group is too large, and the spherical aberration and image curvature generated during the focusing process are insufficiently corrected by the third lens group G3 of the auxiliary focus group, resulting in a decrease in performance at 1.0 times, especially the image curvature is difficult to correct. If the lower limit of the conditional expression (7) is exceeded, although the third lens group G3 of the auxiliary focus group provides sufficient aberration correction, it will offset the movement effect of the second lens group G2 of the main focus group, and the focusing movement will increase, causing the entire optical system to become very large, making it difficult to miniaturize.

[0043] The beneficial effects of the utility model are:

[0044] The utility model provides a shift macro lens, which realizes a maximum field angle of more than 45° while controlling the volume, and a sufficiently large image field of more than 65mm, which exceeds the image field diameter of 20mm of a full-frame camera. The lens and the camera can be shifted relative to each other by more than ±10mm and tilted by more than ±8°, and there will be no black edge occlusion caused by insufficient image field. It can be widely used in professional photography fields such as commodity photography, architecture, and landscape. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 This is an optical structure diagram of the first embodiment of the utility model;

[0046] Figure 2 The spherical aberration, field curvature aberration, distortion aberration and lateral chromatic aberration at infinity, 0.5-times photographic magnification and 1.0-times photographic magnification of the first embodiment;

[0047] Figure 3 This is an optical structure diagram of the second embodiment of the utility model;

[0048] Figure 4 The spherical aberration, field curvature aberration, distortion aberration and lateral chromatic aberration at infinity, 0.5-times photographic magnification and 1.0-times photographic magnification of the second embodiment;

[0049] Figure 5 This is an optical structure diagram of the third embodiment of the utility model;

[0050] Figure 6 The spherical aberration, field curvature aberration, distortion aberration, and lateral chromatic aberration at infinity, 0.5-times magnification, and 1.0-times magnification of the third embodiment are shown. DETAILED DESCRIPTION

[0051] In order to make the purpose, technical solution and advantages of the embodiment of the utility model clearer, the technical solution in the embodiment of the utility model will be further described in detail below in conjunction with the drawings in the embodiment of the utility model. Obviously, the described embodiment is a part of the embodiment of the utility model but not all. Based on the embodiment of the utility model, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the utility model.

[0052] First embodiment:

[0053] like Figure 1 As shown, the macro lens of the first embodiment includes, from the object side, a first lens group G1 with negative refractive power, a positive refractive power G2 and a third lens group G3 with negative refractive power. The front part G1a of the first lens group G1 is composed of two continuous negative lenses. The image field diameter reaches Φ67mm, which is 23.8mm larger than the full-frame image field diameter of 43.2mm. It can achieve a vertical and horizontal translation of more than ±10mm. At the same time, BF_I NF is long enough, and the distance between the optical system and the image plane is large enough, so the shift mechanism of translation and shaking of the head is easy to achieve without causing interference.

[0054] The spherical aberration, field curvature aberration, distortion aberration and lateral chromatic aberration at infinity, 0.5x magnification and 1.0x magnification of the first embodiment are as follows: Figure 2 The data of the first embodiment are as follows: R (mm): radius of curvature of each surface. D (mm): distance between each lens and lens thickness. Nd: refractive index of each glass of d line. Vd: Abbe number of glass.

[0055] Focal length: 55.02.

[0056] FNO: 2.87.

[0057] Half-frame angle ω: 31.543.

[0058]

[0059]

[0060] focal length 55.0179 0.5 times 1.0 times D(6) 47.3370 27.0548 1.0500 D(19) 1.4700 6.7287 9.8404 BF 46.8077 61.8312 84.7243

[0061] Second embodiment:

[0062] like Figure 3As shown, the macro lens of the second embodiment includes, from the object side, a first lens group G1 with negative refractive power, a positive refractive power G2 and a third lens group G3 with negative refractive power. The front part G1a of the first lens group G1 is composed of two continuous negative lenses. The image field diameter reaches Φ67mm, which is 23.8mm larger than the full-frame image field diameter of 43.2mm. It can achieve a vertical and horizontal translation of more than ±10mm. At the same time, BF_I NF is long enough, and the distance between the optical system and the image plane is large enough, so the shift mechanism of translation and shaking of the head is easy to achieve without causing interference.

[0063] The spherical aberration, field curvature aberration, distortion aberration and chromatic aberration of magnification at infinity, 0.5 times photographic magnification and 1.0 times photographic magnification of the second embodiment are as follows: Figure 4 shown.

[0064] The data of the second embodiment are as follows.

[0065] R (mm): The radius of curvature of each surface.

[0066] D(mm): The distance between each lens and the thickness of the lens.

[0067] Nd: The refractive index of each glass at the d line.

[0068] Vd: Abbe number of glass.

[0069] Focal length: 70.02.

[0070] FNO: 2.87.

[0071] Half-frame angle ω: 25.431.

[0072] Surface number R D d Vd 1 8233.8824 1.7000 1.49700 81.61 2 55.2213 12.0292 3 -154.9866 1.0000 1.60034 34.59 4 106.6426 0.3816 5 86.7294 10.0134 1.88300 40.80 6 -185.3510 D(6) 7 90.5329 3.0000 1.88300 40.80 8 inf 0.1500 9 37.5565 3.5000 1.88300 40.80 10 51.9731 3.5651 11 -68.3557 2.1513 1.84278 23.36 12 25.4480 7.2000 1.92286 20.88 13 -99.9414 1.9454 14 239.5532 1.0000 1.84666 23.78 15 24.5947 6.5000 1.49700 81.61 16 -105.4024 0.1500 17 73.3323 2.6005 1.81789 45.12 18 -727.8712 1.4100 19STOP inf D(19) 20 119.1023 1.0000 1.63074 43.74 21 28.7234 7.8347 22 -88.5671 1.0000 1.49700 81.61 23 24.1219 3.5000 1.55562 61.93 24 151.6337 6.9910 25 193.5012 3.0000 1.88300 40.80 26 -113.5784 BF

[0073] focal length 70.0199 0.5 times 1.0 times D(6) 48.9739 26.4411 1.0500 D(19) 1.4700 7.8901 12.6356 BF 50.0767 66.1894 86.8350

[0074] Third embodiment:

[0075] like Figure 5 As shown, the macro lens of the second embodiment includes, from the object side, a first lens group G1 with negative refractive power, a positive refractive power G2 and a third lens group G3 with negative refractive power. The front part G1a of the first lens group G1 is composed of two continuous negative lenses. The image field diameter reaches Φ67mm, which is 23.8mm larger than the full-frame image field diameter of 43.2mm. It can achieve a vertical and horizontal translation of more than ±10mm. At the same time, BF_I NF is long enough, and the distance between the optical system and the image plane is large enough, so the shift mechanism of translation and shaking of the head is easy to achieve without causing interference.

[0076] The spherical aberration, field curvature aberration, distortion aberration and lateral chromatic aberration at infinity, 0.5x magnification and 1.0x magnification of the third embodiment are as follows: Figure 6 shown.

[0077] The data of the third embodiment are as follows.

[0078] R (mm): The radius of curvature of each surface.

[0079] D(mm): The distance between each lens and the thickness of the lens.

[0080] Nd: The refractive index of each glass at the d line.

[0081] Vd: Abbe number of glass.

[0082] Focal length: 47.084.

[0083] FNO: 2.87.

[0084] Half-frame angle ω: 35.612.

[0085]

[0086]

[0087] focal length 47.0839 0.5 times 1.0 times D(6) 43.9504 24.9780 1.0500 D(19) 1.4700 5.7175 7.1928 BF 47.7929 62.5178 84.9705

[0088] (Conditional summary table)

[0089]

[0090]

[0091] The above contents are merely examples and explanations of the structure of the utility model. 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 utility model or exceed the scope defined in the claims, they should all fall within the protection scope of the utility model.

Claims

1. A tilt-shift macro lens, characterized in that: The lens group includes, from the object side to the image side, a first lens group G1 with negative refractive power, a second lens group G2 with positive refractive power, and a third lens group G3 with negative refractive power; The aperture Stop is disposed between the second lens group G2 and the third lens group G3; The first lens group G1 is fixed, the second lens group G2 is used as a main focus lens group, and moves from the image side to the object side, and the third lens group G3 is used as an auxiliary focus group to correct the aberration caused by the movement of the second lens group G2; The front part of the first lens group G1 is composed of negative refractive power G1a, whose focal length is F1a, and satisfies the following conditions (1) and (2): 0.6≤|F1a / F0|≤1.0 (1) 0.5≤F2 / F0≤1.2 (2) in, F1a: focal length of the front part G1a of the first lens group; F0: focal length of the entire optical system at infinity; F2: focal length of the second lens group G2.

2. The tilt-shift macro lens according to claim 1, characterized in that: The setting position of the aperture stop and the length of the back focus satisfy conditional expressions (3) and (4); 0.3≤LS / Ymax≤1.0 (3) 0.6≤|F0 / BF_INF|≤1.6 (4) in, LS: The distance from the aperture stop to the rearmost surface of the image plane of the optical system at infinity; BF_INF: back focal length of the optical system at infinity; Ymax: the maximum paraxial image height at infinity; Ymax = F0 × tanω; ω: half field of view angle at infinity.

3. The tilt-shift macro lens according to claim 1, characterized in that: In the infinite state, the distance between the first lens group G1 and the second lens group G2 satisfies the conditional formula (5); 0.4≤|D12 / F0|≤1.2 (5) in, D12: The distance between the first lens group G1 and the second lens group G2 at infinity.

4. The tilt-shift macro lens according to claim 1, characterized in that: The movement amounts of the second lens group G2 and the third lens group G3 satisfy conditional expressions (6) and (7); 1.0≤|S2_A / S3_A|≤1.7 (6) 0.8≤|S2_B / S3_B|≤1.6 (7) in, S2_A: the focus movement amount of the second lens group G2 when the photographic distance is from infinity to the photographic magnification of 0.5 times; S3_A: the focus movement amount of the third lens group G3 when the photographic distance is from infinity to the photographic magnification of 0.5 times; S2_B: the focus movement amount of the second lens group G2 when the photographic distance is from infinity to the photographic magnification of 1.0 times; S3_B: The focus movement amount of the third lens group G3 when the photographic distance is from infinity to the photographic magnification of 1.0.

Images