Compact internal focusing photographic lens

Abstract

The present invention provides a compact internally focused photographic lens, which sequentially includes, from the object side to the image side: a first lens group with positive optical power, an aperture stop, a second lens group with positive optical power, and a third lens group with negative optical power; during the focusing process from infinity to close range, the second lens group moves along the optical axis towards the object side, and the first lens group and the third lens group remain unchanged in position relative to the image plane; the first lens group satisfies the following conditional formula: 1 ≤ F1 / F ≤ 3.1, (1); the second lens group includes a cemented lens and a singlet, and satisfies the following conditional formula: 0.8 ≤ F2 / F ≤ 3, (2); where F represents the focal length of the photographic lens, F1 represents the combined focal length of the first lens group, and F2 represents the combined focal length of the second lens group. The present invention focuses by means of the movement of an internal singlet group, and through reasonable optical design, good imaging quality and a compact lens size are achieved.

Description

Technical Field

[0001] The present invention relates to the field of optical imaging technology, and particularly to a compact internally focusing photographic lens. Background Art

[0002] In recent years in the photography market, the demand for mirrorless cameras is expanding rapidly. Compared with single-lens reflex cameras which are large in size and poor in portability, mirrorless cameras are small, lightweight and excellent in portability due to the cancellation of the reflex mirror assembly. At the same time, thanks to the increasing development and maturity of high-precision CMOS chips, the resolution of cameras is also increasing day by day, making mirrorless cameras also have good high-quality imaging quality.

[0003] Currently, for interchangeable photographic lenses on the market, in order to obtain high imaging quality, there are generally problems such as large size, heavy weight and poor portability. Prolonged use will cause fatigue to users. Especially in the domestic market, there is a lack of compact photographic lenses that can balance imaging quality and portability. In view of this problem, the present invention provides a compact internally focusing photographic lens. Summary of the Invention

[0004] In view of the deficiencies of the prior art and market demands, the present invention provides a compact internally focusing photographic lens, which has good imaging quality, a compact size, and focuses by means of the movement of an internal single lens group, and has the characteristic of fast focusing speed.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A compact internally focusing photographic lens sequentially includes, along the optical axis from the object side to the image side: a first lens group with positive optical power, an aperture stop, a second lens group with positive optical power, and a third lens group with negative optical power; during the focusing process from infinity to close range, the second lens group moves along the optical axis towards the object side direction, and the first lens group and the third lens group remain unchanged with respect to the position of the image plane;

[0007] The first lens group satisfies the following conditional formula:

[0008] 1≤F1 / F≤3.1, (1);

[0009] The second lens group includes a cemented lens and a single lens, and satisfies the following conditional formula:

[0010] 0.8≤F2 / F≤3, (2);

[0011] Wherein, F represents the focal length of the photographic lens, F1 represents the combined focal length of the first lens group, and F2 represents the combined focal length of the second lens group.

[0012] As a preferred embodiment, the first lens group is composed of a first lens with a negative focal power, a second lens with a positive focal power, a third lens with a positive focal power, and a fourth lens with a negative focal power, which are arranged in sequence from the object side to the image side. Among them, the first lens and the second lens are combined into a cemented lens group, and the third lens and the fourth lens are combined into a cemented lens group.

[0013] As a preferred embodiment, the first lens and the second lens satisfy the following conditional expressions:

[0014] 0.43 ≥ |nd1 - nd2| ≥ 0.17, (3);

[0015] 35.2 ≥ |Vd1 - Vd2| ≥ 2.7, (4);

[0016] Wherein, nd1 is defined as the refractive index of the first lens with respect to light of a wavelength of 587.6 nm, and nd2 is defined as the refractive index of the second lens with respect to light of a wavelength of 587.6 nm; Vd1 is the Abbe number of the first lens with respect to light of a wavelength of 587.6 nm; Vd2 is the Abbe number of the second lens with respect to light of a wavelength of 587.6 nm.

[0017] As a preferred embodiment, the third lens and the fourth lens satisfy the following conditional expressions:

[0018] 31 ≥ |Vd3 - Vd4| ≥ 18, (5);

[0019] Wherein, Vd3 is the Abbe number of the third lens with respect to light of a wavelength of 587.6 nm; Vd4 is the Abbe number of the fourth lens with respect to light of a wavelength of 587.6 nm.

[0020] As a preferred embodiment, the second lens group is composed of a fifth lens with a negative focal power, a sixth lens with a positive focal power, and a seventh lens with a positive focal power, which are arranged in sequence from the object side to the image side. The fifth lens and the sixth lens are combined into a cemented lens group.

[0021] As a preferred embodiment, the fifth lens and the sixth lens satisfy the following conditional expressions:

[0022] 0.2 ≥ |nd5 - nd6| ≥ 0.1, (6);

[0023] Wherein, nd5 is defined as the refractive index of the fifth lens with respect to light of a wavelength of 587.6 nm, and nd6 is defined as the refractive index of the sixth lens with respect to light of a wavelength of 587.6 nm.

[0024] As a preferred embodiment, the seventh lens is a plastic aspherical lens.

[0025] As a preferred solution, the third lens group is composed of an eighth lens with a positive focal power, a ninth lens with a negative focal power, and a tenth lens with a negative focal power, which are arranged in sequence from the object side to the image side.

[0026] As a preferred solution, the eighth lens and the ninth lens form a cemented lens group, and the tenth lens is a meniscus negative lens bent towards the object side.

[0027] As a preferred solution, the second lens group is composed of a fifth lens with a positive focal power, a sixth lens with a negative focal power, and a seventh lens with a positive focal power, which are arranged in sequence from the object side to the image side. The fifth lens and the sixth lens are combined into a cemented lens group, and the cemented surface of the cemented lens group is bent towards the object side.

[0028] Compared with the prior art, the present invention has the following technical effects:

[0029] Through the design of the first lens group, the second lens group, and the third lens group, the present invention realizes an interchangeable photographic lens with good imaging quality, compact size, convenient to carry, and capable of achieving rapid focusing.

[0030] To more clearly illustrate the structural features, technical means, and the specific purposes and functions achieved by the present invention, the following further elaborates on the present invention in detail with reference to the accompanying drawings and specific embodiments: Description of the Drawings

[0031] Figure 1 It is a schematic structural diagram of Embodiment 1 of the present invention;

[0032] Figure 2 It is a schematic diagram of spherical aberration when Embodiment 1 of the present invention is focused at infinity;

[0033] Figure 3 It is a schematic diagram of field curvature when Embodiment 1 of the present invention is focused at infinity;

[0034] Figure 4 It is a schematic diagram of distortion when Embodiment 1 of the present invention is focused at infinity;

[0035] Figure 5 It is a schematic diagram of spherical aberration when Embodiment 1 of the present invention is focused at the nearest focusing distance;

[0036] Figure 6 It is a schematic diagram of field curvature when Embodiment 1 of the present invention is focused at the nearest focusing distance;

[0037] Figure 7 It is a schematic diagram of distortion when Embodiment 1 of the present invention is focused at the nearest focusing distance;

[0038] Figure 8 It is a schematic structural diagram of Embodiment 2 of the present invention;

[0039] Figure 9 It is a schematic diagram of spherical aberration when the focus of Embodiment 2 of the present invention is at infinity;

[0040] Figure 10 It is a schematic diagram of field curvature when the focus of Embodiment 2 of the present invention is at infinity;

[0041] Figure 11 It is a schematic diagram of distortion when the focus of Embodiment 2 of the present invention is at infinity;

[0042] Figure 12 It is a schematic diagram of spherical aberration when the focus of Embodiment 2 of the present invention is at the nearest focusing distance;

[0043] Figure 13 It is a schematic diagram of field curvature when the focus of Embodiment 2 of the present invention is at the nearest focusing distance;

[0044] Figure 14 It is a schematic diagram of distortion when the focus of Embodiment 2 of the present invention is at the nearest focusing distance;

[0045] Figure 15 It is a schematic diagram of the structure of Embodiment 3 of the present invention;

[0046] Figure 16 It is a schematic diagram of spherical aberration when the focus of Embodiment 3 of the present invention is at infinity;

[0047] Figure 17 It is a schematic diagram of field curvature when the focus of Embodiment 3 of the present invention is at infinity;

[0048] Figure 18 It is a schematic diagram of distortion when the focus of Embodiment 3 of the present invention is at infinity;

[0049] Figure 19 It is a schematic diagram of spherical aberration when the focus of Embodiment 3 of the present invention is at the nearest focusing distance;

[0050] Figure 20 It is a schematic diagram of field curvature when the focus of Embodiment 3 of the present invention is at the nearest focusing distance;

[0051] Figure 21 It is a schematic diagram of distortion when the focus of Embodiment 3 of the present invention is at the nearest focusing distance. Detailed implementation manners

[0052] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the invention and simplifying the description, rather than indicating or implying that the indicated position or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention.

[0053] As Figure 1-21 described, a compact internal focusing photographic lens of the present invention sequentially includes, from the object side to the image side along the optical axis: a first lens group G1 with positive optical power, an aperture stop STP, a second lens group G2 with positive optical power, and a third lens group G3 with negative optical power; during the focusing process from infinity to a close distance, the second lens group G2 moves along the optical axis towards the object side direction, and the first lens group G1 and the third lens group G3 remain unchanged in position relative to the image plane IMG. The first lens group G1 satisfies the following conditional formula:

[0054] 1 ≤ F1 / F ≤ 3.1, (1);

[0055] The second lens group G2 includes a cemented lens and a singlet lens, and satisfies the following conditional formula:

[0056] 0.8 ≤ F2 / F ≤ 3, (2);

[0057] Wherein, F represents the focal length of the photographic lens, F1 represents the combined focal length of the first lens group G1, and F2 represents the combined focal length of the second lens group G2.

[0058] Embodiment 1

[0059] Figure 1 Shown is a schematic structural diagram of the compact internal focusing photographic lens of Embodiment 1,

[0060] In this embodiment, the first lens group G1 is composed of a first lens L11 with negative optical power, a second lens L12 with positive optical power, a third lens L13 with positive optical power, and a fourth lens L14 with negative optical power, which are sequentially arranged from the object side to the image side. Among them, the first lens L11 and the second lens L12 are combined into a cemented lens group, and the third lens L13 and the fourth lens L14 are combined into a cemented lens group.

[0061] The first lens L11 and the second lens L12 in the first lens group G1 satisfy the following conditional formula:

[0062] 0.43 ≥ |nd1 - nd2| ≥ 0.17, (3);

[0063] 35.2 ≥ |Vd1 - Vd2| ≥ 2.7, (4);

[0064] Among them, nd1 is defined as the refractive index of the first lens L11 in the first lens group G1 with respect to light with a wavelength of 587.6 nm, and nd2 is defined as the refractive index of the second lens L12 in the first lens group G1 with respect to light with a wavelength of 587.6 nm; Vd1 is the Abbe number of the first lens L11 with respect to light with a wavelength of 587.6 nm; Vd2 is the Abbe number of the second lens L12 with respect to light with a wavelength of 587.6 nm.

[0065] The third lens L13 and the fourth lens L14 in the first lens group G1 satisfy the following conditional expressions:

[0066] 31 ≥ |Vd3 - Vd4| ≥ 18, (5);

[0067] Among them, Vd3 is the Abbe number of the third lens L13 in the first lens group G1 with respect to light with a wavelength of 587.6 nm; Vd4 is the Abbe number of the fourth lens L14 in the first lens group G1 with respect to light with a wavelength of 587.6 nm.

[0068] The second lens group G2 is composed of a fifth lens L21 with a negative optical power, a sixth lens L22 with a positive optical power, and a seventh lens L23 with a positive optical power, which are arranged in sequence from the object side to the image side. The fifth lens L21 and the sixth lens L22 are combined into a cemented lens group, and the seventh lens L23 is a plastic aspherical lens.

[0069] The fifth lens L21 and the sixth lens L22 in the second lens group G2 satisfy the following conditional expressions:

[0070] 0.2 ≥ |nd5 - nd6| ≥ 0.1, (6);

[0071] Among them, nd5 is defined as the refractive index of the fifth lens L21 in the second lens group G2 with respect to light with a wavelength of 587.6 nm, and nd6 is defined as the refractive index of the sixth lens L22 in the second lens group G2 with respect to light with a wavelength of 587.6 nm.

[0072] The third lens group G3 is composed of an eighth lens L31 with a positive optical power, a ninth lens L32 with a negative optical power, and a tenth lens L33 with a negative optical power, which are arranged in sequence from the object side to the image side. The eighth lens L31 and the ninth lens L32 form a cemented lens group, and the tenth lens L33 is a meniscus negative lens and bends towards the stop STP.

[0073] The numerical data of the photographic lens of Embodiment 1 are shown in Tables 1, 2, and 3:

[0074] Table 1

[0075]

[0076]

[0077] Table 2

[0078]

[0079] Table 3

[0080]

[0081] Among them, the surface number indicates the surface numbers of the lenses from the object side to the image side;

[0082] Figures 2-4 It is the spherical aberration, field curvature, and distortion curve diagrams of Example 1 at infinity focus, Figures 5-7 It is the spherical aberration, field curvature, and distortion curve diagrams of Example 1 at the closest focusing distance.

[0083] The spherical aberration curve diagram represents the spherical aberration curve at an f-number of 2.9. Among them, the F-line, D-line, and C-line represent the spherical aberration at wavelengths of 486 nm, 587 nm, and 656 nm respectively. The abscissa represents the magnitude of the spherical aberration value, and the ordinate represents the field of view. The field curvature curve diagram represents the field curvature curve at a semi-field angle ω of 9.5 0 °, where the solid line S represents the value of the chief ray d-line on the sagittal image plane, the solid line T represents the value of the chief ray d-line on the meridional image plane, the abscissa represents the magnitude of the field curvature value, and the ordinate represents the field of view. The distortion curve diagram represents the distortion curve at a semi-field angle ω of 45.8 0 °, where the abscissa represents the distortion value and the ordinate represents the field of view. The above descriptions of various spherical aberration, field curvature, and distortion curve diagrams are the same as those of other embodiments and will not be repeated hereinafter. As can be seen from FIGS. 2-7, the compact internal focusing type photographic lens of this Example 1 has a good imaging effect.

[0084] Example 2

[0085] Figure 8 Shown is the structural schematic diagram of the compact internal focusing type photographic lens of Example 2. The difference between this Example 2 and Example 1 lies in the different lens parameters.

[0086] The numerical data of the said compact internal focusing type photographic lens are shown in Tables 4, 5, and 6:

[0087] Table 4

[0088]

[0089]

[0090] Table 5

[0091]

[0092] Table 6

[0093]

[0094] Figures 9-11 It is the spherical aberration, field curvature, and distortion curve graph when Example 2 is focused at infinity. Figures 12-14 It is the spherical aberration, field curvature, and distortion curve graph when Example 2 is focused at the closest distance. As can be seen from FIGS. 9-14, the compact internal focusing type photographic lens of this embodiment has a good imaging effect.

[0095] Example 3

[0096] Figure 15 The figure shows a schematic structural diagram of the compact internal focusing type photographic lens of Example 3. The difference between this Example 3 and the above-mentioned examples is that in addition to the different lens parameters of the lens, the fifth lens L21 in the second lens group G2 in this Example 3 has a positive optical power, the sixth lens L22 has a negative optical power, the fifth lens L21 and the sixth lens L22 are combined into a cemented lens group, and the cemented surface of the cemented lens group is bent towards the object side.

[0097] The numerical data of the compact internal focusing type photographic lens of this Example 3 are shown in Tables 7, 8, and 9:

[0098] Table 7

[0099]

[0100]

[0101] Table 8

[0102]

[0103] Table 9

[0104]

[0105]

[0106] Figures 16-21 It is the spherical aberration, field curvature, and distortion curve graph when Example 3 is focused at infinity. Figures 16-18 It is the spherical aberration, field curvature, and distortion curve graph when Example 3 is focused at the closest distance. As can be seen from FIGS. 19-21, the compact internal focusing type photographic lens of this embodiment has a good imaging effect.

[0107] Table 10 is a list of the calculated values of conditional expressions 1-4 and Vd for each embodiment:

[0108] Table 10

[0109]

[0110] The foregoing has shown and described the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments, and what is described in the above embodiments and the specification is only to illustrate the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will also have various changes and improvements, and these changes and improvements fall within the scope of the present invention claimed. The scope of the present invention claimed is defined by the appended claims and their equivalents.

Claims

1. A compact internally focused photographic lens, characterized in that, It consists of, in order from the object side to the image side along the optical axis: a first lens group with positive refractive power, an aperture stop, a second lens group with positive refractive power, and a third lens group with negative refractive power; during the focusing process from infinity to a close distance, the second lens group moves along the optical axis towards the object side, and the positions of the first lens group and the third lens group remain unchanged relative to the image plane. The first lens group satisfies the following conditional expressions: 1 ≤ F1 / F ≤ 3.1, (1); The second lens group includes a cemented lens and a singlet lens, and satisfies the following conditional expressions: 0.8 ≤ F2 / F ≤ 3, (2); where F represents the focal length of the photographic lens, F1 represents the combined focal length of the first lens group, and F2 represents the combined focal length of the second lens group; The first lens group consists of a first lens with negative refractive power, a second lens with positive refractive power, a third lens with positive refractive power, and a fourth lens with negative refractive power, which are arranged in order from the object side to the image side. The second lens group consists of a fifth lens, a sixth lens, and a seventh lens, which are arranged in order from the object side to the image side, and the fifth lens and the sixth lens form a cemented lens group. The third lens group consists of an eighth lens with positive refractive power, a ninth lens with negative refractive power, and a tenth lens with negative refractive power, which are arranged in order from the object side to the image side.

2. The compact internally focused photographic lens according to claim 1, wherein The first lens and the second lens form a cemented lens group, and the third lens and the fourth lens form a cemented lens group.

3. The compact internally focusing photographic lens according to claim 2, wherein, The first lens and the second lens satisfy the following conditional expressions: 0.43 ≥ |nd1 - nd2| ≥ 0.17, (3); 35.2 ≥ |Vd1 - Vd2| ≥ 2.7, (4); where nd1 is defined as the refractive index of the first lens with respect to light with a wavelength of 587.6 nm, nd2 is defined as the refractive index of the second lens with respect to light with a wavelength of 587.6 nm; Vd1 is the Abbe number of the first lens with respect to light with a wavelength of 587.6 nm; Vd2 is the Abbe number of the second lens with respect to light with a wavelength of 587.6 nm.

4. The compact internally focused photographic lens according to claim 2, wherein, The third lens and the fourth lens satisfy the following conditional expressions: 31 ≥ |Vd3 - Vd4| ≥ 18, (5); where Vd3 is the Abbe number of the third lens with respect to light with a wavelength of 587.6 nm; Vd4 is the Abbe number of the fourth lens with respect to light with a wavelength of 587.6 nm.

5. The compact internally focused photographic lens according to claim 1, wherein, The second lens group consists of a fifth lens with negative refractive power, a sixth lens with positive refractive power, and a seventh lens with positive refractive power, which are arranged in order from the object side to the image side, and the fifth lens and the sixth lens form a cemented lens group.

6. The compact internally focused photographic lens according to claim 5, wherein, The fifth lens and the sixth lens satisfy the following conditional expressions: 0.2 ≥ |nd5 - nd6| ≥ 0.1, (6); where nd5 is defined as the refractive index of the fifth lens with respect to light with a wavelength of 587.6 nm, nd6 is defined as the refractive index of the sixth lens with respect to light with a wavelength of 587.6 nm.

7. The compact internal focusing photographic lens according to claim 5, wherein The seventh lens is a plastic aspherical lens.

8. The compact internally focused photographic lens according to claim 1, wherein, The eighth lens and the ninth lens form a cemented lens group, and the tenth lens is a meniscus negative lens bent towards the object side.

9. The compact internal focusing photographic lens according to claim 1, wherein The second lens group is composed of a fifth lens with positive optical power, a sixth lens with negative optical power, and a seventh lens with positive optical power, which are arranged in sequence from the object side to the image side. The fifth lens and the sixth lens are combined into a cemented lens group, and the cemented surface of the cemented lens group is bent towards the object side.

Images