Prime lens and imaging device

Abstract

The invention relates to the field of optics, in particular to a prime lens and an imaging device. The prime lens consists of a first lens group with positive focal power and a second lens group with positive wide angle in sequence from an object plane side to an image plane side; the first lens group is sequentially composed of a first lens with negative focal power and a second lens with positive focal power from the object plane side to the image plane side. The prime lens at most comprises a group of glued lenses; the prime lens satisfies the following conditional expressions: fno is less than 2.3; tTL is less than 25 mm; wherein fno is the number of apertures of the prime lens, and TTL is the total optical length of the prime lens. Through the limitation of the structure and parameters, the small size of the prime lens is realized through the arrangement of fewer lens groups, and meanwhile, through the arrangement of fewer glued lenses, the dissipation of light among the lenses is reduced, and the number of apertures of the prime lens is increased.

Description

Technical Field

[0001] The present invention relates to the field of optics, and in particular to a fixed-focus lens and an imaging device. Background Art

[0002] A prime lens is a lens with a fixed focal length, no focal length, or only a field of view. A prime lens does not have a zoom function.

[0003] The design of a fixed-focus lens is much simpler than that of a zoom lens, but generally a zoom lens will have some impact on the imaging during the zooming process. The biggest advantage of a fixed-focus lens over a zoom lens is its fast focusing speed and stable imaging quality.

[0004] Although existing fixed-focus lenses can cover various focal lengths, for a certain fixed-focus lens at a specific focal length, such as a fixed-focus lens with a small focal length, the number of lenses will be continuously increased in order to increase the resolution of the fixed-focus lens, which will cause the fixed-focus lens to become darker and the zoom lens to become larger. Therefore, how to increase the aperture number of the fixed-focus lens and reduce the size of the fixed-focus lens without reducing the resolution of the fixed-focus lens has become an urgent problem to be solved. Summary of the invention

[0005] The present invention will solve the existing technical problems and provide a fixed-focus lens and an imaging device. Through the above-mentioned structure and parameter limitations and the setting of fewer lens groups, a small volume of the fixed-focus lens is achieved. At the same time, through the setting of fewer glued lenses, the dissipation of light between lenses is reduced, and the aperture number of the fixed-focus lens is increased.

[0006] The technical solution provided by the present invention is as follows:

[0007] A fixed-focus lens, which is composed of a first lens group with positive optical power and a second lens group with positive wide angle in order from the object plane side to the image plane side;

[0008] The first lens group is composed of a first lens with negative optical power and a second lens with positive optical power from the object plane side to the image plane side;

[0009] The fixed-focus lens includes at most one set of cemented lenses;

[0010] The fixed-focus lens satisfies the following conditional formula:

[0011] fno<2.3;

[0012] TTL<25mm;

[0013] Wherein, fno is the aperture number of the fixed-focus lens, and TTL is the total optical length of the fixed-focus lens.

[0014] In the technical solution, through the limitation of the above-mentioned structure and parameters and the setting of fewer lens groups, a small volume of the fixed-focus lens is achieved. At the same time, through the setting of fewer glued lenses, the dissipation of light between lenses is reduced, and the aperture number of the fixed-focus lens is increased.

[0015] Preferably, the fixed-focus lens satisfies the following conditional formula:

[0016] 4mm<f<5mm;

[0017] 1.5<fG2 / f<2;

[0018] Wherein, f is the focal length of the fixed-focus lens, and fG2 is the focal length of the second lens group.

[0019] In the present technical solution, by limiting the focal length of the fixed-focus lens, limiting the focal length of the second lens group reduces the possibility that the focal lengths of the remaining lens groups in the fixed-focus lens are too large or too small, reduces the thickness of the lenses in the lens group, and realizes the miniaturization of the fixed-focus lens.

[0020] Preferably, the second lens group consists of, from the object plane side to the image plane side, a third lens with positive focal power, a fourth lens with negative focal power, a fifth lens, a sixth lens with positive focal power, and a cementation of the fifth lens and the sixth lens.

[0021] Preferably, the second lens group satisfies the following conditional formula:

[0022] 2<f56 / f<4;

[0023] Among them, f56 is the combined focal length of the fifth lens and the sixth lens after being glued together.

[0024] In this technical solution, by limiting the combined focal length of the fifth lens and the sixth lens after being glued together, the chromatic aberration and astigmatism of the fixed-focus lens are greatly improved, and the imaging quality is improved.

[0025] Preferably, the first lens group satisfies the following conditional formula:

[0026] 0.15<L2 / TTL<0.25;

[0027] Wherein, L2 is the total optical length of the second lens.

[0028] In this technical solution, by increasing the total optical length of the second lens, the number of lenses in the first lens group in the fixed-focus lens is reduced, thereby achieving miniaturization of the fixed-focus lens.

[0029] Preferably, the second lens group satisfies the following conditional formula:

[0030] 0.3<D6I / TTL<0.4;

[0031] Wherein, D6I is the distance between the sixth lens and the image plane.

[0032] In this technical solution, by limiting the distance between the sixth lens and the image plane, the incident angle of the light of the sixth lens when entering the image plane is reduced, the dissipation of light when entering the image plane is reduced, and the aperture number of the fixed-focus lens is increased.

[0033] Preferably, the optical power of the fifth lens is negative;

[0034] The second lens group satisfies the following conditional formula:

[0035] 0.15<L3 / TTL<0.2;

[0036] Wherein, L3 is the total optical length of the third lens.

[0037] In this technical solution, by limiting the total optical length of the third lens, the space utilization rate in the fixed-focus lens is increased, thereby increasing the resolution of the fixed-focus lens.

[0038] One of the objectives of the present invention is to provide an imaging device, comprising: a fixed-focus lens; and an imaging element configured to receive an image formed by the fixed-focus lens.

[0039] Compared with the prior art, the fixed-focus lens and imaging device provided by the present invention have the following beneficial effects:

[0040] 1. Through the limitation of the above structure and parameters, a small volume of the fixed-focus lens is achieved by setting fewer lens groups. At the same time, by setting fewer cemented lenses, the dissipation of light between lenses is reduced, and the aperture number of the fixed-focus lens is increased.

[0041] 2. By limiting the focal length of the fixed-focus lens, the limitation of the focal length of the second lens group reduces the possibility that the focal length of the remaining lens groups in the fixed-focus lens is too large or too small, reduces the thickness of the lenses in the lens group, and realizes the miniaturization of the fixed-focus lens.

[0042] 3. By increasing the total optical length of the second lens, the number of lenses in the first lens group in the fixed-focus lens is reduced, thereby achieving miniaturization of the fixed-focus lens. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The preferred implementation scheme will be described below in a clear and understandable manner with reference to the accompanying drawings to further illustrate the above-mentioned characteristics, technical features, advantages and implementation methods of a fixed-focus lens and an imaging device.

[0044] Figure 1 It is a structural schematic diagram of a fixed-focus lens of the present invention;

[0045] Figure 2 is an aberration diagram of a fixed-focus lens of the present invention;

[0046] Figure 3 is a coma diagram of a fixed-focus lens of the present invention;

[0047] Figure 4 is a schematic structural diagram of another fixed-focus lens of the present invention;

[0048] Figure 5 is an aberration diagram of another fixed-focus lens of the present invention;

[0049] Figure 6 It is a coma diagram of another fixed-focus lens of the present invention.

[0050] Description of the accompanying drawings: G1, first lens group; G2, second lens group; G3, auxiliary component; L1, first lens; L2, second lens; L3, third lens; L4, fourth lens; L5, fifth lens; L6, sixth lens; STO, aperture; CG1, first protective glass; CG2, second protective glass. DETAILED DESCRIPTION

[0051] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0052] In order to simplify the drawings, only the parts related to the invention are schematically shown in each figure, and they do not represent the actual structure of the product. In addition, in order to simplify the drawings and facilitate understanding, in some figures, only one of the parts with the same structure or function is schematically drawn or marked. In this article, "one" not only means "only one", but also means "more than one".

[0053] Example 1

[0054] like Figure 1 and Figure 4 As shown, a fixed-focus lens, the fixed-focus lens is composed of a first lens group G1 with positive refractive power and a second lens group G2 with positive wide angle in sequence from the object plane side to the image plane side;

[0055] The first lens group G1 is composed of a first lens L1 with negative refractive power and a second lens L2 with positive refractive power in order from the object plane side to the image plane side;

[0056] The fixed-focus lens includes at most one set of cemented lenses;

[0057] The fixed-focus lens satisfies the following conditional formula:

[0058] fno<2.3;

[0059] TTL<25mm;

[0060] Wherein, fno is the aperture number of the fixed-focus lens, and TTL is the total optical length of the fixed-focus lens.

[0061] In this embodiment, through the limitation of the above-mentioned structure and parameters, a small volume of the fixed-focus lens is achieved by setting a smaller number of lens groups. Meanwhile, by setting a smaller number of cemented lenses, the dissipation of light between lenses is reduced, thereby increasing the aperture number of the fixed-focus lens.

[0062] The fixed-focus lens satisfies the following conditional formula:

[0063] 4mm<f<5mm;

[0064] 1.5<fG2 / f<2;

[0065] Among them, f is the focal length of the fixed-focus lens, and fG2 is the focal length of the second lens group G2.

[0066] In this embodiment, by limiting the focal length of the fixed-focus lens, the limitation of the focal length of the second lens group G2 reduces the possibility of the focal length of the remaining lens groups in the fixed-focus lens being too large or too small, reduces the thickness of the lenses in the lens group, and realizes the miniaturization of the fixed-focus lens.

[0067] The second lens group G2 is composed of a third lens L3 with positive power, a fourth lens L4 with negative power, a fifth lens L5, a sixth lens L6 with positive power, and a cementation of the fifth lens L5 and the sixth lens L6 from the object plane side to the image plane side.

[0068] The second lens group G2 satisfies the following conditional formula:

[0069] The second lens group G2 satisfies the following conditional formula:

[0070] 2<f56 / f<4;

[0071] Wherein, f56 is the combined focal length of the fifth lens L5 and the sixth lens L6 after being glued together.

[0072] Wherein, f56 is the combined focal length of the fifth lens L5 and the sixth lens L6 after being glued together.

[0073] In this embodiment, by limiting the combined focal length of the fifth lens L5 and the sixth lens L6 after being glued together, the chromatic aberration and astigmatism of the fixed-focus lens are greatly improved, thereby improving the quality of imaging.

[0074] The first lens group G1 satisfies the following conditional formula:

[0075] 0.15<L2 / TTL<0.25;

[0076] Wherein, L2 is the total optical length of the second lens L2.

[0077] In this embodiment, by increasing the total optical length of the second lens L2, the number of lenses in the first lens group G1 in the fixed-focus lens is reduced, thereby achieving miniaturization of the fixed-focus lens.

[0078] The second lens group G2 satisfies the following conditional formula:

[0079] 0.3<D6I / TTL<0.4;

[0080] Wherein, D6I is the distance between the sixth lens L6 and the image plane.

[0081] In this embodiment, by limiting the distance between the sixth lens L6 and the image plane, the incident angle of the light of the sixth lens L6 when entering the image plane is reduced, the dissipation of the light when entering the image plane is reduced, and the aperture number of the fixed-focus lens is increased.

[0082] The refractive power of the fifth lens L5 is negative;

[0083] The second lens group G2 satisfies the following conditional formula:

[0084] 0.15<L3 / TTL<0.2;

[0085] Wherein, L3 is the total optical length of the third lens L3.

[0086] By limiting the total optical length of the third lens L3, the space utilization rate within the fixed-focus lens is increased, thereby increasing the resolution of the fixed-focus lens.

[0087] Example 2

[0088] like Figures 1 to 3 As shown, a fixed-focus lens, which is composed of a first lens group G1 with positive refractive power, a second lens group G2 with positive wide angle, and an auxiliary component G3 in sequence from the object side to the image side;

[0089] The first lens group G1 is composed of a first lens L1 with negative refractive power and a second lens L2 with positive refractive power in order from the object plane side to the image plane side;

[0090] The second lens group G2 is composed of a third lens L3 with positive power, a fourth lens L4 with negative power, a fifth lens L5 with negative power, a sixth lens L6 with positive power from the object plane side to the image plane side, and the fifth lens L5 and the sixth lens L6 are cemented together.

[0091] The auxiliary component G3 is composed of a first cover glass CG1 and a second cover glass CG2.

[0092] Table 1 shows basic lens data of the fixed focus lens of this example, and Table 2 shows aspherical surface coefficients.

[0093] The surface number column shows the surface number when the surface on the object side is set as the first surface and the numbers are increased one by one toward the image side; the surface type column shows the surface type of a certain lens; the curvature radius column shows the curvature radius of a certain lens, and when the curvature radius is positive, it indicates that the surface is curved toward the object side, and when the curvature radius is negative, it indicates that the surface is curved toward the image side; the center thickness column shows the surface spacing on the optical axis between each surface and the surface adjacent to its image side; the refractive index column shows the refractive index of a certain lens; and the Abbe number column shows the Abbe number of a certain lens.

[0094] In Table 2, K is the cone coefficient, and e is the scientific notation, for example, e-05 represents 10 -5 .

[0095]

Table 1

[0096]

[0097]

[0098]

Table 2

[0099]

[0100] In this embodiment, f=4.01 mm, fno=2.25, TTL=22.2 mm;

[0101] Wherein, f is the focal length of the fixed-focus lens, fno is the aperture number of the fixed-focus lens, and TTL is the total optical length of the fixed-focus lens.

[0102] fG2=7.71mm;

[0103] fG2 / f=1.92;

[0104] Wherein, fG2 is the focal length of the second lens group G2.

[0105] f56=8.24mm; f56 / f=3.66;

[0106] Wherein, f56 is the combined focal length of the fifth lens L5 and the sixth lens L6 after being glued together.

[0107] L2=4.24mm; L2 / TTL=0.19;

[0108] Wherein, L2 is the total optical length of the second lens L2.

[0109] D6I=7.47mm, D6I / TTL=0.336;

[0110] Wherein, D6I is the distance between the sixth lens L6 and the image plane.

[0111] L3=3.78mm, L3 / TTL=0.17;

[0112] Wherein, L3 is the total optical length of the third lens L3.

[0113] Example 3

[0114] like Figures 4 to 5 As shown, a fixed-focus lens, which is composed of a first lens group G1 with positive refractive power, a second lens group G2 with positive wide angle, and an auxiliary component G3 in sequence from the object side to the image side;

[0115] The first lens group G1 is composed of a first lens L1 with negative refractive power and a second lens L2 with positive refractive power in order from the object plane side to the image plane side;

[0116] The second lens group G2 is composed of, from the object side to the image side, a third lens L3 with positive power, a fourth lens L4 with negative power, a fifth lens L5 with positive power, a sixth lens L6 with positive power, and the fifth lens L5 and the sixth lens L6 are cemented together.

[0117] The auxiliary component G3 is composed of a first cover glass CG1 and a second cover glass CG2.

[0118] Table 3 shows basic lens data of the fixed-focus lens of this example, and Table 4 shows aspherical surface coefficients.

[0119] The surface number column shows the surface number when the surface on the object side is set as the first surface and the numbers are increased one by one toward the image side; the surface type column shows the surface type of a certain lens; the curvature radius column shows the curvature radius of a certain lens, and when the curvature radius is positive, it indicates that the surface is curved toward the object side, and when the curvature radius is negative, it indicates that the surface is curved toward the image side; the center thickness column shows the surface spacing on the optical axis between each surface and the surface adjacent to its image side; the refractive index column shows the refractive index of a certain lens; and the Abbe number column shows the Abbe number of a certain lens.

[0120] In Table 4, K is the cone coefficient, and e is the scientific notation, for example, e-05 represents 10 -5 .

[0121]

Table 3

[0122] Face number Surface type Curvature radius / mm Center thickness / mm Refractive Index Abbe number OBJ S1 Aspheric 12.25 1.05 1.54 55.99 S2 Aspheric 2.84 2.05 S3 Aspheric -8.18 4.93 1.66 20.38 S4 Aspheric -6.27 0.10 S5 Spherical INF 2.43 S6 Spherical 9.77 1.15 1.44 95.10 S7 Spherical -6.17 0.14 S8 Aspheric -227.16 0.33 1.64 23.92 S9 Aspheric 3.71 0.42 S10 Aspheric 3.86 0.33 1.64 23.50 S11 Aspheric 4.37 1.80 1.54 55.99 S12 Aspheric -9.99 3.67 S13 Spherical INF 0.30 1.52 64.21 S14 Spherical INF 2.00 S15 Spherical INF 0.50 1.52 64.21 S16 Spherical INF 1.00 IMG

[0123]

Table 4

[0124]

[0125] In this embodiment, f=4.01 mm, fno=2.07, TTL=22.21 mm;

[0126] Wherein, f is the focal length of the fixed-focus lens, fno is the aperture number of the fixed-focus lens, and TTL is the total optical length of the fixed-focus lens.

[0127] fG2=7.5mm;

[0128] fG2 / f=1.87;

[0129] Wherein, fG2 is the focal length of the second lens group G2.

[0130] f56=5.31mm; f56 / f=2.57;

[0131] Wherein, f56 is the combined focal length of the fifth lens L5 and the sixth lens L6 after being glued together.

[0132] L2=4.93mm; L2 / TTL=0.222;

[0133] Wherein, L2 is the total optical length of the second lens L2.

[0134] D6I=7.47mm, D6I / TTL=0.336;

[0135] Wherein, D6I is the distance between the sixth lens L6 and the image plane.

[0136] Example 4

[0137] An imaging device, such as Figures 1 to 6 As shown, it includes: a fixed-focus lens as described in any of the above embodiments, and an imaging element configured to receive an image formed by the fixed-focus lens.

[0138] It should be noted that the above embodiments can be freely combined as needed. The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered as the protection scope of the present invention.

Claims

1. A fixed-focus lens, characterized in that: The fixed-focus lens is composed of a first lens group with positive optical power and a second lens group with positive wide angle in sequence from the object plane side to the image plane side; The first lens group is composed of a first lens with negative optical power and a second lens with positive optical power from the object plane side to the image plane side; The fixed-focus lens includes at most one set of cemented lenses; The fixed-focus lens satisfies the following conditional formula: fno<2.3; TTL<25mm; Wherein, fno is the aperture number of the fixed-focus lens, and TTL is the total optical length of the fixed-focus lens.

2. The fixed-focus lens according to claim 1, characterized in that: The fixed-focus lens satisfies the following conditional formula: 4mm<f<5mm; 1.5<fG2 / f<2; Among them, f is the focal length of the fixed-focus lens, and fG2 is the focal length of the second lens group.

3. The fixed-focus lens according to claim 1, characterized in that: The second lens group is composed of a third lens with positive power, a fourth lens with negative power, a fifth lens, a sixth lens with positive power, and a cementation of the fifth lens and the sixth lens from the object plane side to the image plane side.

4. The fixed-focus lens according to claim 3, characterized in that: The second lens group satisfies the following conditional formula: 2<f56 / f<4; Among them, f56 is the combined focal length of the fifth lens and the sixth lens after being glued together.

5. The fixed-focus lens according to claim 1, characterized in that: The first lens group satisfies the following conditional formula: 0.15<L2 / TTL<0.25; Wherein, L2 is the total optical length of the second lens.

6. The fixed-focus lens according to claim 3, characterized in that: The second lens group satisfies the following conditional formula: 0.3<D6I / TTL<0.4; Wherein, D6I is the distance between the sixth lens and the image plane.

7. The fixed-focus lens according to claim 3, characterized in that: The fifth lens has a negative refractive power; The second lens group satisfies the following conditional formula: 0.15<L3 / TTL<0.2; Wherein, L3 is the total optical length of the third lens.

8. An imaging device, characterized in that: include: The fixed focus lens according to any one of claims 1 to 7; and an imaging element configured to receive an image formed by the fixed-focus lens.

Images