Fixed focal length lens

Abstract

The present invention relates to a fixed-focus lens, comprising: a first lens (L1) and a second lens (L2) arranged in sequence along the direction from the object side to the image side of the optical axis, both of which have negative focal powers; a third lens (L3), a fourth lens (L4) and a fifth lens (L5) all of which have positive focal powers; a sixth lens (L6) with a negative focal power; a seventh lens (L7) with a positive focal power; an eighth lens (L8); and a ninth lens (L9) with a positive focal power, and further comprising: a stop (STO) located between the third lens (L3) and the fourth lens (L4) or on the object side of the fourth lens (L4), and the focal power of the eighth lens (L8) is positive. The fixed-focus lens can be used both day and night without infrared, realizes low-light imaging, and has an ultra-large aperture of F1.0, higher resolution and larger image height.

Description

Technical Field

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

[0002] Driven by the digital information age, the demand for fixed-focus lenses in the fields of security, public safety and monitoring facilities is increasing. Fixed-focus lenses are widely used in various fields due to their advantages of clear imaging, wide monitoring field of view and low illumination requirements. However, ensuring clear imaging at night or in environments with insufficient lighting conditions is still a technical challenge that needs to be overcome in the security field.

[0003] Most high-quality night imaging lenses on the market use a large aperture of F1.4 combined with infrared fill light. However, due to the small infrared imaging range, color information cannot be restored, making research on low-light lenses imperative.

[0004] The prior art CN211293429U discloses a fixed-focus lens, comprising a first lens to a ninth lens arranged in sequence from the object side to the image side along the optical axis. Among them, the first, second, sixth and eighth lenses all have negative optical focal lengths, the third, fourth, fifth, seventh and ninth lenses all have positive optical focal lengths, and the first lens to the ninth lens are all glass spherical lenses. Through the design of the above structure, the performance of the lens reaches more than 12 million pixels, and the aperture FNo2.0, day and night confocality are achieved, the imaging target surface reaches 1 / 2.5 inches, and the F-Theta distortion is less than 10%. However, this fixed-focus lens does not have the characteristics of low-light imaging. Summary of the invention

[0005] In order to overcome the defects in the above-mentioned prior art, the purpose of the present invention is to provide a fixed-focus lens that can be used both day and night without infrared, realize low-light imaging and has an F1.0 ultra-large aperture, higher resolution and larger image height.

[0006] To achieve the above-mentioned object of the invention, the present invention provides a fixed-focus lens, comprising: a first lens and a second lens, both of which have negative optical powers, arranged in sequence along the direction from the object side to the image side of the optical axis; a third lens, a fourth lens and a fifth lens, both of which have positive optical powers; a sixth lens with negative optical power; a seventh lens, an eighth lens and a ninth lens, both of which have positive optical powers, and also comprising: an aperture stop located between the third lens and the fourth lens or on the object side surface of the fourth lens.

[0007] According to one aspect of the present invention, along the direction from the object side to the image side of the optical axis,

[0008] The first lens and the ninth lens are both convex-concave lenses;

[0009] The second lens is a concave-convex lens;

[0010] The third lens, the fourth lens, the fifth lens and the seventh lens are all convex-convex lenses;

[0011] The sixth lens is a concave-concave lens;

[0012] The shape of the eighth lens in the paraxial region is concave-convex.

[0013] According to one aspect of the present invention, the first lens, the second lens, the fourth lens, the eighth lens and the ninth lens are all aspherical lenses;

[0014] The third lens, the fifth lens, the sixth lens and the seventh lens are all spherical lenses.

[0015] According to one aspect of the present invention, the first lens, the second lens, the fourth lens, the eighth lens and the ninth lens are all plastic lenses;

[0016] The third lens, the fifth lens, the sixth lens and the seventh lens are all glass lenses.

[0017] According to one aspect of the present invention, the fifth lens, the sixth lens and the seventh lens are cemented together to form a cemented lens.

[0018] According to one aspect of the present invention, the focal length F567 of the cemented lens and the focal length F of the fixed-focus lens satisfy the relationship: 5.2≤F567 / F≤7.6.

[0019] According to one aspect of the present invention, the focal length F567 of the cemented lens and the center thickness db1 of the cemented lens satisfy the relationship: 0.2≤db1 / F567≤0.3.

[0020] According to one aspect of the present invention, the total optical length TTL of the fixed-focus lens and the focal length F of the fixed-focus lens satisfy the relationship: 6.5≤TTL / F≤7.3.

[0021] According to one aspect of the present invention, the optical back focus BFL of the fixed-focus lens and the focal length F of the fixed-focus lens satisfy the relationship: 0.9≤BFL / F≤1.1.

[0022] According to one aspect of the present invention, the focal length F1 of the first lens and the focal length F4 of the fourth lens satisfy the relationship: -2.4≤F4 / F1≤-2.

[0023] According to one aspect of the present invention, the focal length F8 of the eighth lens and the focal length F of the fixed-focus lens satisfy the relationship: 8.6≤F8 / F≤12.2.

[0024] According to one aspect of the present invention, the focal length F9 of the ninth lens and the focal length F of the fixed-focus lens satisfy the relationship: 14.6≤F9 / F≤24.4.

[0025] According to one aspect of the present invention, the combined focal length F89 of the eighth lens and the ninth lens and the focal length F of the fixed-focus lens satisfy the relationship: 5.3≤F89 / F≤6.9.

[0026] According to one aspect of the present invention, a center length d23 of the image side surface of the second lens from the object side surface of the third lens, a center length d34 of the image side surface of the third lens from the object side surface of the fourth lens, and a combined focal length F89 of the eighth lens and the ninth lens satisfy the relationship: 0.1≤(d23+d34) / F89≤0.2.

[0027] According to the solution of the present invention, a fixed-focus lens including a total of 9 lenses and an aperture is provided, and the optical powers of the first lens to the ninth lens are "negative-negative-positive-positive-positive-negative-positive-positive-positive" in sequence, and the aperture is arranged between the third lens and the fourth lens or on the object side of the fourth lens in an optical architecture, so as to achieve F1.0 ultra-large aperture, large target surface, low-light imaging, and day and night use without infrared, and no out-of-focus in the temperature range of -40°C to 80°C.

[0028] According to one solution of the present invention, the object side and image side of the above-mentioned nine lenses are designed with different concave and convex shapes, and a cemented lens composed of the fifth lens to the seventh lens is used to effectively correct the chromatic aberration and aberration of the imaging. On this basis, the assembly tolerance sensitivity of the entire optical system is low, and a high resolution of 5 million pixels is achieved. In addition, through the reasonable combination of glass-plastic hybrid lenses, the relevant parameters of specific lenses and the optical total length, optical back focus and other parameters of the fixed-focus lens are reasonably set, so as to achieve low cost, miniaturization and light weight of the fixed-focus lens. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 A schematic diagram schematically shows the optical structure of a fixed-focus lens according to Embodiment 1 of the present invention;

[0030] Figure 2 A schematic diagram schematically shows the optical structure of a fixed-focus lens according to Embodiment 2 of the present invention;

[0031] Figure 3 A schematic diagram schematically shows the optical structure of a fixed-focus lens according to Embodiment 3 of the present invention;

[0032] Figure 4 A schematic diagram schematically shows the optical structure of a fixed-focus lens according to Embodiment 4 of the present invention;

[0033] Figure 5The optical structure diagram of the fixed-focus lens according to Embodiment 5 of the present invention is schematically shown. DETAILED DESCRIPTION

[0034] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0035] When describing the embodiments of the present invention, the orientation or positional relationship expressed by the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" are based on the orientation or positional relationship shown in the relevant drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the above terms should not be understood as limiting the present invention.

[0036] The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments. The embodiments cannot be described one by one here, but the embodiments of the present invention are not therefore limited to the following embodiments.

[0037] Figure 1 The optical structure diagram of a fixed focus lens according to an embodiment of the present invention is schematically shown. Figure 1 As shown, along the direction from the object side to the image side of the optical axis, the fixed-focus lens of the present invention includes: a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, a sixth lens L6, a seventh lens L7, an eighth lens L8 and a ninth lens L9 in sequence. Among them, the first lens L1, the second lens L2 and the sixth lens L6 all have negative focal powers, and the remaining third lens L3, the fourth lens L4, the fifth lens L5, the seventh lens L7, the eighth lens L8 and the ninth lens L9 all have positive focal powers. In addition, the fixed-focus lens also includes an aperture STO. The aperture STO can be set between the third lens L3 and the fourth lens L4, and can also be set on the object side of the fourth lens L4.

[0038] Among the above nine lenses, the object side surfaces of the first lens L1 and the ninth lens L9 are convex, and the image side surfaces are concave. The object side surface of the second lens L2 is concave, and the image side surface is convex. The object side surface and image side surface of the third lens L3, the fourth lens L4, the fifth lens L5 and the seventh lens L7 are convex. The object side surface and image side surface of the sixth lens L6 are concave. The object side surface of the eighth lens L8 near the optical axis of the lens is concave, and the image side surface is convex.

[0039] It can be seen that the fixed-focus lens adopts an optical structure of 9 lenses, and an aperture stop STO is set between the third lens L3 and the fourth lens L4 or on the object side of the fourth lens L4. Figure 1 As shown in the figure, a parallel flat plate CG of a certain thickness is also provided on the image side. The entire fixed-focus lens is thus formed, which can avoid the degradation of image resolution and focus deviation of the fixed-focus lens at high and low temperatures, and realize the F1.0 ultra-large aperture design. At the same time, by making a specific combination design of the positive and negative optical powers of the above-mentioned 9 lenses and the different shapes of the object side and the image side, aberrations and chromatic aberrations can be corrected, the tolerance sensitivity of the optical imaging system can be reduced, the assembly tolerance sensitivity is low, high-pixel low-light imaging can be achieved, and the imaging has a larger image height. In addition, the fixed-focus lens can be used day and night without infrared, and has the performance of not being out of focus in the temperature range of -40℃ to 80℃.

[0040] In terms of lens surface design and material selection, preferably, the first lens L1, the second lens L2, the fourth lens L4, the eighth lens L8 and the ninth lens L9 in the fixed-focus lens are all aspherical lenses, and the materials of the above lenses are all plastic materials. In addition, the third lens L3, the fifth lens L5, the sixth lens L6 and the seventh lens L7 in the fixed-focus lens are all spherical lenses, and the materials of the above lenses are all glass materials. Spherical lenses are set in the above positions in the fixed-focus lens, and the aberrations can be compensated to a certain extent by the above arrangement and the design of the distance between the spherical lenses. Combined with the above aspherical lenses, since the aspherical lenses can compensate for various aberrations such as spherical aberration, coma aberration, distortion aberration, etc., by adjusting the curvature radius R value of the aspherical lens surface, the direction of the incident light is controlled, thereby suppressing the aberration at a low level. By reasonably combining spherical lenses and aspherical lenses, the imaging performance of the large aperture fixed-focus lens of the present invention can be improved. In addition, the optical architecture of 4 glass lenses and 5 plastic lenses can balance the high and low temperature performance of the fixed-focus lens, making the lens low-cost and lightweight.

[0041] In addition, the fifth lens L5, the sixth lens L6 and the seventh lens L7 can be cemented to form a cemented lens. By using a cemented lens, the aberration and chromatic aberration of the entire optical imaging system of the fixed-focus lens can be corrected, the tolerance sensitivity of the optical imaging system can be effectively reduced, and the high resolution of the fixed-focus lens of 5 million pixels can be achieved without out-of-focus in the temperature range of -40°C to 80°C.

[0042] The focal length F567 of the above-mentioned cemented lens and the focal length F of the fixed-focus lens satisfy the relationship: 5.2≤F567 / F≤7.6. The focal length F567 of the cemented lens and its center thickness db1 satisfy the relationship: 0.2≤db1 / F567≤0.3. By limiting the relationship between the focal length of the cemented lens and the focal length of the fixed-focus lens and the relationship between the focal length of the cemented lens and the center thickness, and setting a reasonable range, the chromatic aberration and aberration caused by the light entering through the aperture STO and the fourth lens L4 can be effectively corrected.

[0043] In the present invention, the total optical length TTL of the fixed-focus lens and its focal length F satisfy the relationship: 6.5≤TTL / F≤7.3. The above-mentioned total optical length TTL is the distance from the center of the object side surface to the center of the image side surface of the first lens L1 of the fixed-focus lens. The optical back focus BFL of the fixed-focus lens and its focal length F satisfy the relationship: 0.9≤BFL / F≤1.1. The above-mentioned optical back focus BFL is the distance from the center of the image side surface to the center of the imaging surface of the last lens of the fixed-focus lens, that is, the ninth lens L9. By limiting the above range, the fixed-focus lens can be miniaturized and has the characteristics of small size and high performance.

[0044] In the present invention, the focal length F1 of the first lens L1 and the focal length F4 of the fourth lens L4 satisfy the relationship: -2.4≤F4 / F1≤-2. This can control the light trend of the entire optical imaging system and reduce the aberration caused by the large-angle light entering through the aperture STO.

[0045] In the present invention, the focal length F8 of the eighth lens L8 and the focal length F of the fixed focus lens satisfy the relationship: 8.6≤F8 / F≤12.2. The focal length F9 of the ninth lens L9 and the focal length F of the fixed focus lens satisfy the relationship: 14.6≤F9 / F≤24.4. At the same time, the combined focal length F89 of the eighth lens L8 and the ninth lens L9 and the focal length F of the fixed focus lens satisfy the relationship: 5.3≤F89 / F≤6.9. In this way, distortion can be controlled and reduced, which is conducive to large target surface design.

[0046] In the present invention, the center length d23 of the image side surface of the second lens L2 from the object side surface of the third lens L3, the center length d34 of the image side surface of the third lens L3 from the object side surface of the fourth lens L4, and the combined focal length F89 of the eighth lens L8 and the ninth lens L9 satisfy the relationship: 0.1≤(d23+d34) / F89≤0.2. This is conducive to reducing the sensitivity of the second lens L2, the third lens L3 and the fourth lens L4 to the modulation transfer function (MTF) of the fixed-focus lens, while making the fixed-focus lens structure compact, which is more conducive to miniaturization.

[0047] In summary, the fixed-focus lens of the present invention has an ultra-large aperture of F1.0, which can realize large target surface and low-light imaging, and can be used both day and night without infrared, and is not out of focus in the temperature range of -40°C to 80°C. The use of cemented lenses can effectively correct the chromatic aberration and aberration of imaging. In addition, the assembly tolerance sensitivity of the entire optical system is low. On this basis, a high resolution of 5 million pixels is achieved. At the same time, the fixed-focus lens achieves low cost, miniaturization and light weight.

[0048] The fixed-focus lens of the present invention is specifically described below with five embodiments. In each of the following embodiments, the fixed-focus lens of the present invention comprises nine lenses, an aperture STO, a parallel plate CG, and an image side surface IMA. The aperture STO is recorded as one surface STO, the image side surface IMA is recorded as one surface IMA, and the cemented surface of the three-cemented lens composed of the fifth lens L5, the sixth lens L6, and the seventh lens L7 is recorded as two surfaces. The above nine lenses and the parallel plate CG each have two surfaces.

[0049] Parameters of various embodiments that specifically meet the above relationship are shown in Table 1 below:

[0050]

[0051]

[0052] Table 1

[0053] In the present invention, the aspherical lens of the fixed focus lens satisfies the following formula:

[0054]

[0055] In the above formula, z is the axial distance from the surface to the vertex at a height h perpendicular to the optical axis along the optical axis; c represents the curvature at the vertex of the aspheric surface; k is the quadratic constant of the surface; A4, A6, A8, A 10 , A 12 , A 14 , A 16 ···represent the fourth-order, sixth-order, eighth-order, tenth-order, twelfth-order, fourteenth-order, sixteenth-order···aspheric coefficients respectively.

[0056] Example 1

[0057] See also Figure 1 In this embodiment, the aperture STO is disposed between the third lens L3 and the fourth lens L4.

[0058] The parameters of each lens of the fixed-focus lens of this embodiment include the curvature radius R value, thickness d, refractive index Nd of the material and Abbe number Vd. S1 to S19 represent each surface of each lens, cemented lens, aperture STO and parallel plate CG in the fixed-focus lens, as shown in Table 2 below.

[0059] Surface number Curvature radius R value Thickness d Refractive index Nd Abbe number Vd 1 13.842 2.600 1.54 55.7 2 5.018 4.899 3 -7.320 3.340 1.64 23.4 4 -15.427 2.976 5 28.845 4.720 1.85 23.8 6 -28.845 4.500 7(STO) Infinity -0.527 8 80.000 3.730 1.54 55.7 9 -27.223 0.120 10 31.023 4.430 1.62 63.4 11 -11.850 1.000 1.85 23.8 12 15.834 5.795 1.59 68.6 13 -15.834 0.118 14 -24.344 3.375 1.64 23.4 15 -18.176 0.120 16 9.165 3.300 1.54 55.7 17 9.274 6.336 18 Infinity 0.800 1.52 64.2 19 Infinity 0.200 Image plane Infinity -

[0060] Table 2

[0061] The aspheric coefficients of the aspheric lenses of the fixed focus lens of this embodiment include the fourth-order aspheric coefficient A4, the sixth-order aspheric coefficient A6, the eighth-order aspheric coefficient A8, the tenth-order aspheric coefficient A 10 , 12th-order aspheric coefficient A 12 and the quadratic surface constant K value, as shown in Table 3 below.

[0062] Surf <![CDATA[A4]]> <![CDATA[A6]]> <![CDATA[A8]]> <![CDATA[A 10 ]]> <![CDATA[A 12 ]]> K Value 1 -7.125E-04 1.202E-05 -1.167E-07 6.636E-10 -1.604E-12 -3.371 2 -1.619E-03 1.935E-05 -7.879E-07 1.915E-08 -3.400E-10 -0.426 3 2.301E-04 -3.375E-06 1.029E-07 -3.251E-09 4.672E-11 -1.110 4 3.366E-04 1.666E-07 -2.602E-08 1.324E-09 -1.797E-11 -1.484 8 1.333E-04 -4.277E-07 -1.482E-08 2.053E-10 -1.686E-12 38.493 9 2.203E-04 -8.110E-07 -1.948E-08 2.728E-10 -2.255E-12 -6.517 14 3.360E-04 -9.030E-06 8.476E-08 -8.762E-10 1.993E-12 -70.822 15 7.568E-05 -5.854E-06 4.884E-08 -2.797E-10 3.559E-13 -12.081 16 -4.228E-04 2.194E-07 5.091E-08 -3.567E-11 -9.472E-13 -5.033 17 -5.333E-04 5.867E-06 -1.246E-08 -4.244E-10 6.334E-12 -5.208

[0063] Table 3

[0064] Depend on Figure 1 , combined with the relevant parameters and data in Tables 1, 2 and 3 above, it can be seen that the fixed-focus lens of this embodiment has an ultra-large aperture of 1.0, which can achieve large target surface and low-light imaging, and can be used both day and night without infrared, and is not out of focus in the temperature range of -40°C to 80°C. The use of cemented lenses can effectively correct the chromatic aberration and aberration of imaging. In addition, the assembly tolerance sensitivity of the entire optical system is low. On this basis, a high resolution of 5 million pixels is achieved. At the same time, the fixed-focus lens achieves low cost, miniaturization and light weight.

[0065] Example 2

[0066] See also Figure 2 In this embodiment, the aperture stop STO is arranged on the object side surface of the fourth lens L4.

[0067] The parameters of each lens of the fixed-focus lens of this embodiment include the curvature radius R value, thickness d, refractive index Nd of the material and Abbe number Vd. S1 to S18 represent each surface of each lens, cemented lens, aperture STO and parallel plate CG in the fixed-focus lens, as shown in Table 4 below.

[0068] Surface number Curvature radius R value Thickness d Refractive index Nd Abbe number Vd 1 17.331 2.600 1.54 55.7 2 5.256 4.899 3 -7.567 3.340 1.64 23.4 4 -17.688 2.976 5 27.739 4.720 1.85 23.8 6 -27.739 4.500 7(STO) 80.000 3.730 1.54 55.7 8 -21.316 0.120 9 52.693 4.430 1.62 63.4 10 -12.128 1.000 1.85 23.8 11 14.744 5.795 1.59 68.6 12 -14.744 0.118 13 -18.693 3.375 1.64 23.4 14 -14.022 0.120 15 10.044 3.300 1.54 55.7 16 10.341 7.017 17 Infinity 0.800 1.52 64.2 18 Infinity 0.200 Image plane Infinity -

[0069] Table 4

[0070] The aspheric coefficients of the aspheric lenses of the fixed focus lens of this embodiment include the fourth-order aspheric coefficient A4, the sixth-order aspheric coefficient A6, the eighth-order aspheric coefficient A8, the tenth-order aspheric coefficient A 10 , 12th-order aspheric coefficient A 12and the quadratic surface constant K value, as shown in Table 5 below.

[0071]

[0072]

[0073] Table 5

[0074] Depend on Figure 2 , combined with the relevant parameters and data in Table 1, Table 4 and Table 5 above, it can be seen that the fixed-focus lens of this embodiment has an ultra-large aperture of F1.0, which can achieve large target surface and low-light imaging, and can be used both day and night without infrared, and is not out of focus in the temperature range of -40℃ to 80℃. The use of cemented lenses can effectively correct the chromatic aberration and aberration of imaging. In addition, the assembly tolerance sensitivity of the entire optical system is low. On this basis, a high resolution of 5 million pixels is achieved. At the same time, the fixed-focus lens achieves low cost, miniaturization and light weight.

[0075] Example 3

[0076] See also Figure 3 In this embodiment, the aperture STO is disposed between the third lens L3 and the fourth lens L4.

[0077] The parameters of each lens of the fixed-focus lens of this embodiment include the curvature radius R value, thickness d, refractive index Nd of the material and Abbe number Vd. S1 to S19 represent each surface of each lens, cemented lens, aperture STO and parallel plate CG in the fixed-focus lens, as shown in Table 6 below.

[0078] Surface number Curvature radius R value Thickness d Refractive index Nd Abbe number Vd 1 14.841 2.600 1.54 55.7 2 5.094 4.899 3 -7.308 3.340 1.64 23.4 4 -15.382 2.976 5 28.781 4.720 1.85 23.8 6 -28.781 4.500 7(STO) Infinity -0.527 8 80.000 3.730 1.54 55.7 9 -25.443 0.120 10 31.933 4.430 1.62 63.4 11 -11.935 1.000 1.85 23.8 12 15.665 5.795 1.59 68.6 13 -15.665 0.118 14 -23.251 3.375 1.64 23.4 15 -17.266 0.120 16 9.693 3.300 1.54 55.7 17 9.667 6.318 18 Infinity 0.800 1.52 64.2 19 Infinity 0.200 Image plane Infinity -

[0079] Table 6

[0080] The aspheric coefficients of the aspheric lenses of the fixed focus lens of this embodiment include the fourth-order aspheric coefficient A4, the sixth-order aspheric coefficient A6, the eighth-order aspheric coefficient A8, the tenth-order aspheric coefficient A 10 , 12th-order aspheric coefficient A 12 , 14th-order aspheric coefficient A 14 and the quadratic surface constant K value, as shown in Table 7 below.

[0081]

[0082]

[0083] Table 7

[0084] Depend on Figure 3, combined with the relevant parameters and data in Table 1, Table 6 and Table 7 above, it can be seen that the fixed-focus lens of this embodiment has an ultra-large aperture of 1.0, which can achieve large target surface and low-light imaging, and can be used both day and night without infrared, and is not out of focus in the temperature range of -40℃ to 80℃. The use of cemented lenses can effectively correct the chromatic aberration and aberration of imaging. In addition, the assembly tolerance sensitivity of the entire optical system is low. On this basis, a high resolution of 5 million pixels is achieved. At the same time, the fixed-focus lens achieves low cost, miniaturization and light weight.

[0085] Example 4

[0086] See also Figure 4 In this embodiment, the aperture STO is disposed between the third lens L3 and the fourth lens L4.

[0087] The parameters of each lens of the fixed-focus lens of this embodiment include the curvature radius R value, thickness d, refractive index Nd of the material and Abbe number Vd. S1 to S19 represent each surface of each lens, cemented lens, aperture STO and parallel plate CG in the fixed-focus lens, as shown in Table 8 below.

[0088] Surface number Curvature radius R value Thickness d Refractive index Nd Abbe number Vd 1 14.206 2.600 1.54 55.7 2 5.035 4.899 3 -7.248 3.340 1.64 23.4 4 -15.333 2.976 5 28.661 4.720 1.85 23.8 6 -28.661 4.500 7(STO) Infinity -0.527 8 80.000 3.730 1.54 55.7 9 -25.858 0.120 10 31.501 4.430 1.62 63.4 11 -11.816 1.000 1.85 23.8 12 15.707 5.795 1.59 68.6 13 -15.707 0.118 14 -23.403 3.375 1.64 23.4 15 -17.000 0.120 16 9.786 3.300 1.54 55.7 17 9.663 6.301 18 Infinity 0.800 1.52 64.2 19 Infinity 0.200 Image plane Infinity -

[0089] Table 8

[0090] The aspheric coefficients of the aspheric lenses of the fixed focus lens of this embodiment include the fourth-order aspheric coefficient A4, the sixth-order aspheric coefficient A6, the eighth-order aspheric coefficient A8, the tenth-order aspheric coefficient A 10 , 12th-order aspheric coefficient A 12 , 14th-order aspheric coefficient A 14 and the quadratic surface constant K value, as shown in Table 9 below.

[0091]

[0092]

[0093] Table 9

[0094] Depend on Figure 4 , combined with the relevant parameters and data in Table 1, Table 8 and Table 9 above, it can be seen that the fixed-focus lens of this embodiment has an ultra-large aperture of F1.0, which can achieve large target surface and low-light imaging, and can be used both day and night without infrared, and is not out of focus in the temperature range of -40℃ to 80℃. The use of cemented lenses can effectively correct the chromatic aberration and aberration of imaging. In addition, the assembly tolerance sensitivity of the entire optical system is low. On this basis, a high resolution of 5 million pixels is achieved. At the same time, the fixed-focus lens achieves low cost, miniaturization and light weight.

[0095] Example 5

[0096] See also Figure 5 In this embodiment, the aperture STO is disposed between the third lens L3 and the fourth lens L4.

[0097] The parameters of each lens of the fixed-focus lens of this embodiment include the curvature radius R value, thickness d, refractive index Nd of the material and Abbe number Vd. S1 to S19 represent each surface of each lens, cemented lens, aperture STO and parallel plate CG in the fixed-focus lens, as shown in Table 10 below.

[0098] Surface number Curvature radius R value Thickness d Refractive index Nd Abbe number Vd 1 15.102 2.600 1.54 55.7 2 5.096 4.899 3 -7.319 3.340 1.64 23.4 4 -15.369 2.976 5 28.756 4.720 1.85 23.8 6 -28.756 4.500 7(STO) Infinity -0.527 8 80.000 3.730 1.54 55.7 9 -24.668 0.120 10 32.433 4.430 1.62 63.4 11 -11.989 1.000 1.85 23.8 12 15.426 5.795 1.59 68.6 13 -15.426 0.118 14 -23.214 3.375 1.64 23.4 15 -17.034 0.120 16 9.840 3.300 1.54 55.7 17 9.695 6.229 18 Infinity 0.800 1.52 64.2 19 Infinity 0.200 Image plane Infinity -

[0099] Table 10

[0100] The aspheric coefficients of the aspheric lenses of the fixed focus lens of this embodiment include the fourth-order aspheric coefficient A4, the sixth-order aspheric coefficient A6, the eighth-order aspheric coefficient A8, the tenth-order aspheric coefficient A 10 , 12th-order aspheric coefficient A 12 , 14th-order aspheric coefficient A 14 and the quadratic surface constant K value, as shown in Table 11 below.

[0101]

[0102]

[0103] Table 11

[0104] Depend on Figure 5 , combined with the relevant parameters and data in Table 1, Table 10 and Table 11 above, it can be seen that the fixed-focus lens of this embodiment has an ultra-large aperture of F1.0, which can achieve large target surface and low-light imaging, and can be used both day and night without infrared, and is not out of focus in the temperature range of -40℃ to 80℃. The use of cemented lenses can effectively correct the chromatic aberration and aberration of imaging. In addition, the assembly tolerance sensitivity of the entire optical system is low. On this basis, a high resolution of 5 million pixels is achieved. At the same time, the fixed-focus lens achieves low cost, miniaturization and light weight.

[0105] The above is only one embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A fixed-focus lens, comprising: Arranged in sequence along the optical axis from the object side to the image side are a first lens (L1) and a second lens (L2) both having negative optical powers; a third lens (L3), a fourth lens (L4) and a fifth lens (L5) both having positive optical powers; a sixth lens (L6) having negative optical power; a seventh lens (L7) having positive optical power; and an eighth lens (L8); and a ninth lens (L9) having positive optical power, the lenses having optical power totaling nine, characterized in that they further include: an aperture stop (STO) located between the third lens (L3) and the fourth lens (L4) or on the object side surface of the fourth lens (L4), The optical power of the eighth lens (L8) is positive; The fifth lens (L5), the sixth lens (L6) and the seventh lens (L7) are cemented together to form a cemented lens, and the focal length (F567) of the cemented lens and the focal length (F) of the fixed-focus lens satisfy the relationship: 5.2≤F567 / F≤7.

6.

2. The fixed-focus lens according to claim 1, characterized in that: Along the direction from the object side to the image side of the optical axis, The first lens (L1) and the ninth lens (L9) are both convex-concave lenses; The second lens (L2) is a meniscus lens; The third lens (L3), the fourth lens (L4), the fifth lens (L5) and the seventh lens (L7) are all convex-convex lenses; The sixth lens is a concave-concave lens; The shape of the eighth lens in the paraxial region is concave-convex.

3. The fixed-focus lens according to claim 1, characterized in that: The first lens (L1), the second lens (L2), the fourth lens (L4), the eighth lens (L8) and the ninth lens (L9) are all aspherical lenses; The third lens (L3), the fifth lens (L5), the sixth lens (L6) and the seventh lens (L7) are all spherical lenses.

4. The fixed-focus lens according to claim 1, characterized in that: The first lens (L1), the second lens (L2), the fourth lens (L4), the eighth lens (L8) and the ninth lens (L9) are all plastic lenses; The third lens (L3), the fifth lens (L5), the sixth lens (L6) and the seventh lens (L7) are all glass lenses.

5. The fixed-focus lens according to claim 1, wherein: The focal length (F567) of the cemented lens and the center thickness (db1) of the cemented lens satisfy the relationship: 0.2≤db1 / F567≤0.

3.

6. The fixed-focus lens according to any one of claims 1 to 5, characterized in that: The total optical length (TTL) of the fixed-focus lens and the focal length (F) of the fixed-focus lens satisfy the relationship: 6.5≤TTL / F≤7.

3.

7. The fixed-focus lens according to any one of claims 1 to 5, characterized in that: The optical back focus (BFL) of the fixed-focus lens and the focal length (F) of the fixed-focus lens satisfy the relationship: 0.9≤BFL / F≤1.

1.

8. The fixed-focus lens according to any one of claims 1 to 5, characterized in that: The focal length (F1) of the first lens (L1) and the focal length (F4) of the fourth lens (L4) satisfy the relationship: -2.4≤F4 / F1≤-2.

9. The fixed-focus lens according to any one of claims 1 to 5, characterized in that: The focal length (F8) of the eighth lens (L8) and the focal length (F) of the fixed-focus lens satisfy the relationship: 8.6≤F8 / F≤12.

2.

10. The fixed-focus lens according to any one of claims 1 to 5, characterized in that: The focal length (F9) of the ninth lens (L9) and the focal length (F) of the fixed-focus lens satisfy the relationship: 14.6≤F9 / F≤24.

4.

11. The fixed-focus lens according to any one of claims 1 to 5, characterized in that: The combined focal length (F89) of the eighth lens (L8) and the ninth lens (L9) and the focal length (F) of the fixed-focus lens satisfy the relationship: 5.3≤F89 / F≤6.

9.

12. The fixed-focus lens according to any one of claims 1 to 5, characterized in that: A center length (d23) of the image side surface of the second lens (L2) from the object side surface of the third lens (L3), a center length (d34) of the image side surface of the third lens (L3) from the object side surface of the fourth lens (L4), and a combined focal length (F89) of the eighth lens (L8) and the ninth lens (L9) satisfy the relationship: 0.1≤(d23+d34) / F89≤0.2.

Images