Prime lens

Abstract

The embodiment of the utility model discloses a prime lens. The prime lens comprises a first lens with positive focal power, a second lens with positive focal power, a third lens with positive focal power, a fourth lens with negative focal power, a fifth lens with positive focal power, a sixth lens with negative focal power, a seventh lens with positive focal power and an eighth lens with positive focal power which are sequentially arranged from the object space to the image space along the optical axis; the prime lens further comprises a diaphragm, and the diaphragm is located between the sixth lens and the seventh lens. The prime lens provided by the utility model uses eight lenses to realize clear imaging under a 1 / 2.7 ''target surface and a wave band of 436-870 nm, the aperture is larger, the image quality is higher, day and night confocal is realized, and the prime lens is suitable for use requirements under more conditions.

Description

Technical Field

[0001] The utility model relates to the technical field of lenses, in particular to a fixed-focus lens. Background Art

[0002] As a mainstream product in the security industry, fixed-focus lenses are very popular in the market. However, as the 1 / 1.8″ chip becomes more and more widely applicable, the requirements for the size, aperture, and operating environment of the lens it matches are becoming increasingly stringent. Currently, the mainstream 1 / 1.8″ optical lenses on the market have a small aperture and are too large, which is not conducive to product use and promotion. Therefore, it is necessary to develop a high-image-quality telephoto lens with a large aperture, day and night parfocality, and capable of matching with a 1 / 2.7″ chip. Utility Model Content

[0003] The utility model provides a fixed-focus lens, which uses 8 lenses to achieve clear imaging in the 436nm-870nm band under a 1 / 2.7″ target surface, a larger aperture, higher image quality, and day and night confocality, suitable for use in a wide range of situations.

[0004] The utility model provides a fixed-focus lens, comprising a first lens with positive focal power, a second lens with positive focal power, a third lens with positive focal power, a fourth lens with negative focal power, a fifth lens with positive focal power, a sixth lens with negative focal power, a seventh lens with positive focal power, and an eighth lens with positive focal power, which are arranged in sequence from the object side to the image side along the optical axis;

[0005] The fixed-focus lens further includes an aperture stop, and the aperture stop is located between the sixth lens and the seventh lens.

[0006] Optionally, the effective focal length of the fixed-focus lens at infinity and the total optical length of the fixed-focus lens satisfy:

[0007] 1.112≤TTL / EFL≤1.622;

[0008] Wherein, TTL represents the total optical length of the fixed-focus lens, and EFL represents the effective focal length of the fixed-focus lens at infinity.

[0009] Optionally, the maximum image height of the fixed-focus lens and the back focal length of the fixed-focus lens satisfy:

[0010] 0.732≤BFL / IH≤1.158;

[0011] Wherein, BFL represents the back focal length of the fixed-focus lens; IH represents the maximum imaging height of the fixed-focus lens.

[0012] Optionally, the refractive index of the seventh lens and the Abbe number of the eighth lens satisfy:

[0013] Nd7≤1.95;

[0014] Vd8≤95.00;

[0015] Wherein, Nd7 represents the refractive index of the seventh lens, and Vd8 represents the Abbe number of the eighth lens.

[0016] Optionally, the first lens and the second lens form a first cemented lens group with positive optical power, and the focal length of the first lens and the combined focal length of the first cemented lens group satisfy:

[0017] 0.795≤F1 / F101≤0.849;

[0018] The focal length of the first cemented lens group and the effective focal length of the fixed-focus lens at infinity satisfy:

[0019] 0.768≤F101 / EFL≤1.523;

[0020] Wherein, F1 represents the focal length of the first lens, F101 represents the combined focal length of the first cemented lens group, and EFL represents the effective focal length of the fixed-focus lens at infinity.

[0021] Optionally, the third lens, the sixth lens and the eighth lens are all plastic aspheric lenses.

[0022] Optionally, the focal length of the third lens, the focal length of the sixth lens, the focal length of the eighth lens, and the effective focal length of the fixed-focus lens at infinity satisfy:

[0023] 5.513≤F3 / EFL≤11.151;

[0024] -1.544≤F6 / EFL≤-0.725;

[0025] 0.923≤F8 / EFL≤1.145;

[0026] Wherein, F3, F6 and F8 represent the focal length of the third lens, the focal length of the sixth lens and the focal length of the eighth lens respectively, and EFL represents the effective focal length of the fixed-focus lens at infinity.

[0027] Optionally, the first lens, the second lens, the fourth lens, the fifth lens and the seventh lens are all glass spherical lenses.

[0028] Optionally, the maximum imaging height of the fixed-focus lens and the entrance pupil diameter of the fixed-focus lens satisfy:

[0029] 0.402≤IH / EPD≤0.985;

[0030] Wherein, IH represents the maximum imaging height of the fixed-focus lens; EPD represents the entrance pupil diameter of the fixed-focus lens.

[0031] Optionally, the object side surface of the first lens is convex, the object side surface of the second lens is convex, and the image side surface is concave, the object side surface of the third lens is convex, and the image side surface is concave, the object side surface of the fourth lens is convex, the object side surface of the fifth lens is convex, and the image side surface is concave, the object side surface of the sixth lens is concave, and the image side surface is convex, the object side surface of the seventh lens is convex, and the image side surface is concave, and the object side surface of the eighth lens is convex, and the image side surface is concave.

[0032] The fixed-focus lens provided in an embodiment of the present invention includes a first lens with positive focal power, a second lens with positive focal power, a third lens with positive focal power, a fourth lens with negative focal power, a fifth lens with positive focal power, a sixth lens with negative focal power, a seventh lens with positive focal power, and an eighth lens with positive focal power, arranged in sequence along the optical axis from the object side to the image side. The fixed-focus lens also includes an aperture stop located between the sixth and seventh lenses. The positive focal power of the first and second lenses ensures that light has a larger aperture before entering the aperture stop, thereby increasing the aperture of the fixed-focus lens. Furthermore, the placement of the aperture stop between the sixth lens with negative focal power and the seventh lens with positive focal power allows the fixed-focus lens's higher-order aberrations to be controlled at the front end of the lens, ensuring that image height and target area are increased at the rear end of the lens while maintaining good image quality, thus meeting the requirements of a wider range of use cases. By rationally designing the focal power of each lens, clear imaging can be achieved in the 436nm to 870nm wavelength band on a 1 / 2.7" target surface, with a wider aperture and higher image quality, achieving day and night confocality.

[0033] It should be understood that the content described in this section is not intended to identify the key or important features of the embodiments of the present invention, nor is it intended to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0035] Figure 1 A schematic structural diagram of a fixed-focus lens provided in an embodiment of the present utility model;

[0036] Figure 2A field curvature distortion diagram of a fixed-focus lens provided in an embodiment of the present utility model;

[0037] Figure 3 A ray fan diagram of a fixed-focus lens provided by an embodiment of the present utility model;

[0038] Figure 4 A vertical axis chromatic aberration diagram of a fixed-focus lens provided in an embodiment of the present utility model;

[0039] Figure 5 A schematic structural diagram of another fixed-focus lens provided in an embodiment of the present utility model;

[0040] Figure 6 A field curvature distortion diagram of another fixed-focus lens provided in an embodiment of the present utility model;

[0041] Figure 7 A ray fan diagram of another fixed-focus lens provided by an embodiment of the present utility model;

[0042] Figure 8 A vertical axis chromatic aberration diagram of another fixed-focus lens provided in an embodiment of the present invention

[0043] Figure 9 A schematic structural diagram of another fixed-focus lens provided in an embodiment of the present utility model;

[0044] Figure 10 Field curvature distortion diagram of another fixed-focus lens provided in an embodiment of the present utility model

[0045] Figure 11 A ray fan diagram of another fixed-focus lens provided in an embodiment of the present utility model;

[0046] Figure 12 This is a vertical axis chromatic aberration diagram of another fixed-focus lens provided in an embodiment of the present utility model. DETAILED DESCRIPTION

[0047] In order to help those skilled in the art better understand the present invention, 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 embodiments described 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 making creative efforts should fall within the scope of protection of the present invention.

[0048] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0049] Figure 1 This is a schematic diagram of the structure of a fixed-focus lens provided by an embodiment of the present utility model, with reference to Figure 1 The fixed-focus lens includes a first lens 10 with positive optical power, a second lens 20 with positive optical power, a third lens 30 with positive optical power, a fourth lens 40 with negative optical power, a fifth lens 50 with positive optical power, a sixth lens 60 with negative optical power, a seventh lens 70 with positive optical power and an eighth lens 80 with positive optical power, which are arranged in sequence from the object side to the image side along the optical axis; the fixed-focus lens also includes an aperture 90, which is located between the sixth lens 60 and the seventh lens 70.

[0050] As you can understand, optical power is the reciprocal of focal length and represents an optical system's ability to bend light. The greater the absolute value of the optical power, the greater the light-bending ability, while the smaller the absolute value, the weaker the light-bending ability. When the optical power is a positive number, the light is refracted in a convergent manner; when the optical power is a negative number, the light is refracted in a divergent manner. By setting the optical power of the first lens 10 and the second lens 20 to be positive, a larger diameter is ensured before light enters the aperture 90, thereby increasing the aperture of the fixed-focus lens. In addition, the aperture 90 is placed between the sixth lens 60 with a negative optical power and the seventh lens 70 with a positive optical power. This allows the high-order aberrations of the fixed-focus lens to be controlled at the front end of the lens, ensuring that the image height and target area are increased at the rear end of the lens while maintaining good image quality, meeting the requirements of a wider range of situations. By rationally designing the optical power of each lens, clear imaging can be achieved in the 436nm to 870nm band on a 1 / 2.7" target area, while also achieving a larger aperture and higher image quality, thereby achieving day and night confocality.

[0051] Optionally, the object-side surface of the first lens 10 is convex, the object-side surface of the second lens 20 is convex, and the image-side surface is concave, the object-side surface of the third lens 30 is convex, and the image-side surface is concave, the object-side surface of the fourth lens 40 is convex, the object-side surface of the fifth lens 50 is convex, and the image-side surface is concave, the object-side surface of the sixth lens 60 is concave, and the image-side surface is convex, the object-side surface of the seventh lens 70 is convex, and the image-side surface is concave, and the object-side surface of the eighth lens 80 is convex, and the image-side surface is concave.

[0052] Optionally, the first lens 10 , the second lens 20 , the fourth lens 40 , the fifth lens 50 and the seventh lens 70 are all glass spherical lenses, and the third lens 30 , the sixth lens 60 and the eighth lens 80 are all plastic aspherical lenses.

[0053] Glass spherical lenses are easy to process and have better thermal stability, while plastic aspherical lenses have better aberration correction effects. Designing a glass-plastic hybrid structure can compensate for each other. Using a combination of glass and plastic lenses in a fixed-focus lens can better balance the lens's resolution and improve the imaging effect.

[0054] Optionally, the effective focal length of the fixed-focus lens at infinity and the total optical length of the fixed-focus lens satisfy:

[0055] 1.112≤TTL / EFL≤1.622;

[0056] TTL represents the total optical length of the fixed-focus lens, and EFL represents the effective focal length of the fixed-focus lens at infinity.

[0057] Setting TTL and EFL to satisfy the above relationship allows the fixed-focus lens to meet the optical performance requirements while ensuring that the lens size can be greatly reduced, thereby improving the compatibility of fixed-focus lenses.

[0058] Optionally, the maximum image height of the fixed-focus lens and the back focal length of the fixed-focus lens meet the following requirements:

[0059] 0.732≤BFL / IH≤1.158;

[0060] Where BFL represents the back focal length of the fixed-focus lens; IH represents the maximum imaging height of the fixed-focus lens.

[0061] Setting BFL and IH to satisfy the above relationship can ensure that the fixed-focus lens has a sufficient imaging area while keeping the total optical length of the fixed-focus lens short, which is conducive to miniaturization of the fixed-focus lens.

[0062] Optionally, the refractive index of the seventh lens element 70 and the Abbe number of the eighth lens element 80 satisfy:

[0063] Nd7≤1.95;

[0064] Vd8≤95.00;

[0065] Wherein Nd7 represents the refractive index of the seventh lens element 70 , and Vd8 represents the Abbe number of the eighth lens element 80 .

[0066] The seventh lens element 70 is a glass lens, and the eighth lens element 80 is a plastic lens. Glass and plastic materials can complement each other, and the combination of glass and plastic lenses in a fixed-focus lens effectively balances the image resolution. The seventh lens element 70 is made of a high-refractive-index material, which enhances its ability to deflect light, converging light from each field of view into the aperture 90 at a smaller angle, effectively reducing field-of-view aberrations. The eighth lens element 80 is positioned near the aperture 90, where the intersection points of light rays from each field of view at different lens apertures are close. This position is particularly beneficial for correcting system chromatic aberration, and therefore, a material with a high Abbe number is preferred for the eighth lens element 80.

[0067] Optionally, the first lens 10 and the second lens 20 form a first cemented lens group with positive focal power, and the focal length of the first lens 10 and the combined focal length of the first cemented lens group satisfy:

[0068] 0.795≤F1 / F101≤0.849;

[0069] The focal length of the first cemented lens group and the effective focal length of the fixed focus lens at infinity satisfy:

[0070] 0.768≤F101 / EFL≤1.523;

[0071] Wherein, F1 represents the focal length of the first lens 10, F101 represents the combined focal length of the first cemented lens group, and EFL represents the effective focal length of the fixed-focus lens at infinity.

[0072] Setting the ratio of the focal length F1 of the first lens 10 to the combined focal length F101 of the first cemented lens group within the aforementioned range allows for smoother entry of object-side light into the imaging system, significantly correcting higher-order aberrations. The first lens 10 and the second lens 20 are cemented positive lenses with a convex front and concave rear configuration, meeting the aforementioned requirements and achieving a telephoto effect.

[0073] Optionally, the focal length of the third lens 30, the focal length of the sixth lens 60, the focal length of the eighth lens 80, and the effective focal length of the fixed-focus lens at infinity satisfy:

[0074] 5.513≤F3 / EFL≤11.151;

[0075] -1.544≤F6 / EFL≤-0.725;

[0076] 0.923≤F8 / EFL≤1.145;

[0077] Wherein, F3, F6 and F8 represent the focal length of the third lens 30, the focal length of the sixth lens 60 and the focal length of the eighth lens 80 respectively, and EFL represents the effective focal length of the fixed-focus lens at infinity.

[0078] The third, sixth, and eighth lenses 30, 60, and 80 all utilize plastic aspheric lenses. Setting the focal length of each lens within this range allows light to converge when passing through the aperture and entering the third, sixth, and eighth lenses 30, 60, and 80. This prevents excessive pressure on the remaining lenses during correction of chromatic aberration, aberrations, and the chief ray angle (CRA), which could result in difficult-to-process shapes. Furthermore, the use of aspheric surfaces makes it easier to correct these aberrations. Furthermore, the eighth lens 80 maintains the chief ray angle within a suitable range, and the height of the intersection of the chief ray and the image plane for maximum field of view can be adjusted at the end of the optical system, making it compatible with a variety of chips and saving lens costs.

[0079] Optionally, the maximum image height of the fixed-focus lens and the entrance pupil diameter of the fixed-focus lens meet the following requirements:

[0080] 0.402≤IH / EPD≤0.985;

[0081] Where IH represents the maximum imaging height of the fixed-focus lens; EPD represents the entrance pupil diameter of the fixed-focus lens.

[0082] Setting IH and EPD to satisfy the above relationship can control the entrance pupil diameter of the fixed-focus lens while ensuring a large image plane and high-quality imaging, ensuring sufficient edge field angle of the large-image-plane imaging system and improving image plane brightness.

[0083] In this embodiment, the surface of the aspheric lens satisfies the following formula:

[0084]

[0085] Among them, z is the axial sagittal height of the aspheric surface in the Z direction; r is the height of the aspheric surface; c is the curvature of the fitted sphere, which is the inverse of the curvature radius; k is the fitted cone coefficient; A, B, C, D, E, F, and G are the 4th, 6th, 8th, 10th, 12th, 14th, and 16th order coefficients of the aspheric polynomial, respectively.

[0086] For example, Table 1 shows Figure 1 Specific parameters of the corresponding fixed-focus lens:

[0087] Table 1 Specific parameters of fixed focus lens

[0088] Scope of protection Example 1 Lower limit Upper limit TTL / EFL 1.452 1.112 1.622 BFL / IH 0.874 0.732 1.158 Nd7 1.95 1.80 1.95 Vd8 90.06 40.00 95.00 F1 / F101 0.817 0.795 0.849 F101 / EFL 1.271 0.768 1.523 F3 / EFL 8.134 5.513 11.151 F6 / EFL -1.271 -1.544 -0.725 F8 / EFL 1.046 0.923 1.145 IH / EPD 0.724 0.402 0.985

[0089] Table 2 shows the parameter data of each lens in Example 1. Example 1 can realize a fixed-focus lens with an image plane size of Φ = 7.0 mm, a focal length F = 15.474 mm, an aperture number F# = 1.60, a total lens length TTL = 22.470 mm, and an operating band of 436 nm to 870 nm.

[0090] Table 2 Design values ​​of optical physical parameters of the fixed focus lens of Example 1

[0091] Surface number Surface type Radius of curvature thickness Materials (nd) Material (vd) 1 spherical surface 11.1365 2.2543 1.69 70.41 2 spherical surface 48.9981 0.9430 1.66 62.90 3 spherical surface 53.9744 0.4964 4 Aspheric 19.2363 1.2504 1.61 95.00 5 Aspheric 25.0406 0.1614 6 spherical surface 25.4654 0.8278 1.65 41.50 7 spherical surface 5.1014 2.3321 1.57 62.31 8 spherical surface 55.9254 1.4373 9 Aspheric -3.8561 1.9861 1.63 37.52 10 Aspheric -6.7012 0.6230 11 STO INF 0.0774 12 spherical surface 49.0163 0.8273 1.95 53.19 13 spherical surface 53.1666 0.0750 14 Aspheric 4.4648 3.0606 1.54 90.06 15 Aspheric 6.9074 4.2884 16 spherical surface INF 0.7100 1.52 64.21 17 spherical surface INF 1.1195 18 IMX INF -

[0092] The surface numbers are numbered according to the order of the surfaces of each lens. Surface numbers "2" and "7" are cemented surfaces, "16" and "17" are the two surfaces of the protective glass, "18" is the image surface, and "STO" represents the aperture of a fixed-focus lens. The radius of curvature represents the degree of curvature of the corresponding lens surface. A positive value represents that the surface is bent toward the image side, and a negative value represents that the surface is bent toward the object side. "INF" indicates that the surface is a plane and the radius of curvature is infinite. The thickness represents the axial distance from the center of the current surface to the next surface. The units of the curvature radius and thickness are both mm. Material (nd) represents the refractive index, which represents the ability of the material between the current surface and the next surface to deflect light. A blank space represents that the current position is air and the refractive index is 1. Material (vd) represents the Abbe number, which represents the dispersion characteristics of the material between the current surface and the next surface to light. A blank space represents that the current position is air.

[0093] Table 3 shows the design values ​​of the aspheric parameters in Example 1:

[0094] Surface number k A B C 4 -41.5158 5.010387E-04 -3.023629E-05 5.484273E-07 5 1.3592 -2.648481E-05 -6.861847E-06 -3.857065E-07 9 -4.2833 5.575728E-04 -2.803181E-05 -1.507561E-06 10 -9.7687 -5.294613E-05 -2.595633E-05 -4.211510E-07 14 -0.0161 -1.514198E-03 -1.810233E-04 1.837087E-05 15 0.1018 1.364829E-06 6.086051E-05 -2.324462E-05

[0095] Table 3

[0096] Surface number D E F G 4 -5.985841E-09 -1.346029E-10 5.670733E-12 -4.188411E-14 5 2.441579E-09 4.211879E-10 -7.021509E-12 -5.196223E-14 9 8.162715E-08 5.925276E-09 -2.715986E-10 -1.074180E-11 10 6.551828E-08 2.930505E-09 -2.265910E-10 -7.179018E-12 14 -1.742344E-06 8.250375E-08 -2.559553E-09 6.076092E-11 15 2.300682E-06 -1.169028E-07 2.802892E-09 -1.004206E-11

[0097] 5.010387E-04 means the A coefficient of surface number 4 is 5.010387×10 -4 .

[0098] Figure 2 This is a field curvature distortion diagram of a fixed-focus lens provided in an embodiment of the present utility model. Figure 2 In the coordinate system on the left, the horizontal coordinate represents the magnitude of the field curvature, in mm; the vertical coordinate represents the normalized image height, without unit; T represents the meridian, S represents the arc loss; Figure 2 It can be seen that the lens provided in this embodiment effectively controls the fixed-focus field curvature. That is, when imaging, the difference in image quality between the center and the periphery is small. In the coordinate system on the right, the horizontal coordinate represents the magnitude of the distortion, in %, and the vertical coordinate represents the normalized image height, without a unit.

[0099] Figure 3 The present invention provides a ray fan diagram for a fixed-focus lens. The ray fan diagram is one of the most commonly used evaluation methods in modern optical design. The horizontal axis is the beam diameter, and the vertical axis is the vertical axis aberration. The most ideal curve is a straight line that coincides with the horizontal axis, indicating that all light rays converge at the same point on the image plane. The corresponding interval on the vertical axis of the curve is the maximum diffusion range of the light beam on the ideal image plane. The ray fan diagram can not only reflect the monochromatic aberration of different wavelengths, but also indicate the size of the vertical axis chromatic aberration. Figure 3 It can be seen that the fixed-focus lens is well aligned with the horizontal axis at all wavelengths in all fields of view, indicating that the vertical aberration of each wavelength is well corrected. At the same time, there is no obvious dispersion at each wavelength, indicating that the system chromatic aberration is also well corrected, thus ensuring that the fixed-focus lens can achieve high-resolution imaging requirements.

[0100] Figure 4 This is a vertical axis chromatic aberration diagram of a fixed focus lens provided by an embodiment of the present invention. The vertical axis chromatic aberration curve represents the normalization of the field of view, with 0 representing the optical axis. The main wavelength is 546nm, and the horizontal direction represents the offset relative to the main wavelength in micrometers (μm). Figure 4 It can be seen that the vertical chromatic aberration of different wavelengths is controlled within a good range, indicating that the vertical chromatic aberration of this fixed-focus lens is well controlled and can meet the needs of wide-spectrum applications.

[0101] Figure 5 This is a schematic diagram of the structure of another fixed-focus lens provided by an embodiment of the present utility model. Table 4 is a schematic diagram of the structure of another fixed-focus lens provided by an embodiment of the present utility model. Figure 5 Specific parameters of the corresponding fixed-focus lens:

[0102] Table 4 Specific parameters of fixed-focus lenses

[0103] Scope of protection Example 2 Lower limit Upper limit TTL / EFL 1.368 1.112 1.622 BFL / IH 0.945 0.732 1.158 Nd7 1.84 1.80 1.95 Vd8 65.54 40.00 95.00 F1 / F101 0.818 0.795 0.849 F101 / EFL 1.140 0.768 1.523 F3 / EFL 9.272 5.513 11.151 F6 / EFL -1.135 -1.544 -0.725 F8 / EFL 1.071 0.923 1.145 IH / EPD 0.631 0.402 0.985

[0104] Table 5 shows the parameter data of each lens in Example 2. Example 2 can achieve an image plane size Φ = 6.7 mm, focal length F = 16.993 mm, aperture number F# = 1.59, total lens length TTL = 23.243 mm, and a fixed-focus lens with an operating band of 436 nm to 870 nm.

[0105] Table 5 Design values ​​of optical physical parameters of the fixed focus lens of Example 2

[0106]

[0107]

[0108] The surface numbers are numbered according to the order of the surfaces of each lens. Surface numbers "2" and "7" are cemented surfaces, "16" and "17" are the two surfaces of the protective glass, "18" is the image surface, and "STO" represents the aperture of a fixed-focus lens. The radius of curvature represents the degree of curvature of the corresponding lens surface. A positive value represents that the surface is bent toward the image side, and a negative value represents that the surface is bent toward the object side. "INF" indicates that the surface is a plane and the radius of curvature is infinite. The thickness represents the axial distance from the center of the current surface to the next surface. The units of the curvature radius and thickness are both mm. Material (nd) represents the refractive index, which represents the ability of the material between the current surface and the next surface to deflect light. A blank space represents that the current position is air and the refractive index is 1. Material (vd) represents the Abbe number, which represents the dispersion characteristics of the material between the current surface and the next surface to light. A blank space represents that the current position is air.

[0109] Table 6 shows the design values ​​of the aspheric parameters in Example 2:

[0110]

[0111]

[0112] Table 6

[0113] Surface number D E F G 4 -5.973106E-09 -1.291831E-10 5.863308E-12 -5.826160E-14 5 2.254817E-09 4.090491E-10 -7.598813E-12 -3.432352E-14 9 8.726477E-08 6.345404E-09 -2.539790E-10 -1.699999E-11 10 6.958358E-08 3.225354E-09 -2.347291E-10 -1.332050E-11 14 -1.708474E-06 8.658509E-08 -2.556951E-09 1.139282E-12 15 2.385903E-06 -9.850821E-08 3.358490E-09 -3.582268E-10

[0114] 5.090545E-04 means the A coefficient of surface number 4 is 5.090545×10 -4 .

[0115] Figure 6 This is a field curvature distortion diagram of another fixed-focus lens provided in an embodiment of the present utility model. Figure 6 In the coordinate system on the left, the horizontal coordinate represents the magnitude of the field curvature, in mm; the vertical coordinate represents the normalized image height, without unit; T represents the meridian, S represents the arc loss; Figure 6 It can be seen that the lens provided in this embodiment effectively controls the fixed-focus field curvature. That is, when imaging, the difference in image quality between the center and the periphery is small. In the coordinate system on the right, the horizontal coordinate represents the magnitude of the distortion, in %, and the vertical coordinate represents the normalized image height, without a unit.

[0116] Figure 7 The ray fan diagram of another fixed focus lens provided in the embodiment of the present invention is one of the most commonly used evaluation methods in modern optical design. The horizontal axis is the beam diameter, and the vertical axis is the vertical axis aberration. The most ideal curve is a straight line that coincides with the horizontal axis, indicating that all light rays converge at the same point on the image plane, and the corresponding interval on the vertical axis of the curve is the maximum diffusion range of the light beam on the ideal image plane. The ray fan diagram can not only reflect the monochromatic aberration of different wavelengths, but also indicate the size of the vertical axis chromatic aberration. Figure 7 It can be seen that the fixed-focus lens is well aligned with the horizontal axis at all wavelengths in all fields of view, indicating that the vertical aberration of each wavelength is well corrected. At the same time, there is no obvious dispersion at each wavelength, indicating that the system chromatic aberration is also well corrected, thus ensuring that the fixed-focus lens can achieve high-resolution imaging requirements.

[0117] Figure 8 This is a vertical axis chromatic aberration diagram of another fixed focus lens provided by an embodiment of the present invention. The vertical axis chromatic aberration curve represents the normalized field of view, with 0 representing the optical axis. The main wavelength is 546nm, and the horizontal direction represents the offset relative to the main wavelength in micrometers (μm). Figure 8 It can be seen that the vertical chromatic aberration of different wavelengths is controlled within a good range, indicating that the vertical chromatic aberration of this fixed-focus lens is well controlled and can meet the needs of wide-spectrum applications.

[0118] Figure 9 This is a structural diagram of another fixed-focus lens provided by an embodiment of the present utility model. Table 7 is a schematic diagram of the fixed-focus lens provided by an embodiment of the present utility model. Figure 9 Specific parameters of the corresponding fixed-focus lens:

[0119] Table 7 Specific parameters of fixed-focus lenses

[0120] Scope of protection Example 3 Lower limit Upper limit TTL / EFL 1.282 1.112 1.622 BFL / IH 1.016 0.732 1.158 Nd7 1.95 1.80 1.95 Vd8 65.49 40.00 95.00 F1 / F101 0.807 0.795 0.849 F101 / EFL 1.019 0.768 1.523 F3 / EFL 7.392 5.513 11.151 F6 / EFL -0.998 -1.544 -0.725 F8 / EFL 0.997 0.923 1.145 IH / EPD 0.563 0.402 0.985

[0121] Table 8 shows the parameter data of each lens in Example 3. Example 3 can realize a fixed-focus lens with an image plane size of Φ = 7.0 mm, a focal length F = 19.900 mm, an aperture number F# = 1.61, a total lens length TTL = 25.509 mm, and an operating band of 436 nm to 870 nm.

[0122] Table 8 Design values ​​of optical physical parameters of the fixed focus lens of Example 3

[0123]

[0124]

[0125] The surface numbers are numbered according to the order of the surfaces of each lens. Surface numbers "2" and "7" are cemented surfaces, "16" and "17" are the two surfaces of the protective glass, "18" is the image surface, and "STO" represents the aperture of a fixed-focus lens. The radius of curvature represents the degree of curvature of the corresponding lens surface. A positive value represents that the surface is bent toward the image side, and a negative value represents that the surface is bent toward the object side. "INF" indicates that the surface is a plane and the radius of curvature is infinite. The thickness represents the axial distance from the center of the current surface to the next surface. The units of the curvature radius and thickness are both mm. Material (nd) represents the refractive index, which represents the ability of the material between the current surface and the next surface to deflect light. A blank space represents that the current position is air and the refractive index is 1. Material (vd) represents the Abbe number, which represents the dispersion characteristics of the material between the current surface and the next surface to light. A blank space represents that the current position is air.

[0126] Table 9 shows the design values ​​of the aspheric parameters in Example 3:

[0127] Surface number k A B C 4 -39.0670 5.045334E-04 -2.993124E-05 5.588514E-07 5 1.5578 -2.551832E-05 -6.826691E-06 -3.875230E-07 9 -4.3268 5.193301E-04 -3.226434E-05 -1.497850E-06 10 -10.6194 -1.610240E-05 -2.453853E-05 -3.975045E-07 14 -0.0448 -1.513949E-03 -2.048778E-04 1.752254E-05 15 -0.5960 -1.724910E-04 4.480460E-05 -2.416432E-05

[0128] Table 9

[0129] Surface number D E F G 4 -5.805357E-09 -1.291838E-10 5.556830E-12 -5.702937E-14 5 2.207884E-09 4.188257E-10 -6.920604E-12 -4.350719E-14 9 8.407821E-08 6.393556E-09 -2.240742E-10 -7.987645E-12 10 6.571965E-08 3.225749E-09 -2.001980E-10 -2.368685E-12 14 -1.584502E-06 9.398253E-08 -2.255369E-09 -3.454523E-11 15 2.350589E-06 -9.597257E-08 5.696919E-09 -3.713272E-10

[0130] 5.045334E-04 indicates that the A coefficient of surface number 4 is 5.045334×10 -4 .

[0131] Figure 10 This is a field curvature distortion diagram of another fixed-focus lens provided in an embodiment of the present utility model. Figure 10 In the coordinate system on the left, the horizontal coordinate represents the magnitude of the field curvature, in mm; the vertical coordinate represents the normalized image height, without unit; T represents the meridian, S represents the arc loss; Figure 10 It can be seen that the lens provided in this embodiment effectively controls the fixed-focus field curvature. That is, when imaging, the difference in image quality between the center and the periphery is small. In the coordinate system on the right, the horizontal coordinate represents the magnitude of the distortion, in %, and the vertical coordinate represents the normalized image height, without a unit.

[0132] Figure 11 Another ray fan diagram of a fixed focus lens provided in the embodiment of the present invention is a ray fan diagram, which is one of the most commonly used evaluation methods in modern optical design. The horizontal axis is the beam diameter, and the vertical axis is the vertical axis aberration. The most ideal curve is a straight line that coincides with the horizontal axis, indicating that all light rays converge at the same point on the image plane, and the corresponding interval on the vertical axis of the curve is the maximum diffusion range of the light beam on the ideal image plane. The ray fan diagram can not only reflect the monochromatic aberration of different wavelengths, but also indicate the size of the vertical axis chromatic aberration. Figure 11It can be seen that the fixed-focus lens is well aligned with the horizontal axis at all wavelengths in all fields of view, indicating that the vertical aberration of each wavelength is well corrected. At the same time, there is no obvious dispersion at each wavelength, indicating that the system chromatic aberration is also well corrected, thus ensuring that the fixed-focus lens can achieve high-resolution imaging requirements.

[0133] Figure 12 This is a vertical axis chromatic aberration diagram of another fixed focus lens provided by an embodiment of the present invention. The vertical axis chromatic aberration curve represents the normalization of the field of view, with 0 representing the optical axis. The main wavelength is 546nm, and the horizontal direction represents the offset relative to the main wavelength in micrometers (μm). Figure 12 It can be seen that the vertical chromatic aberration of different wavelengths is controlled within a good range, indicating that the vertical chromatic aberration of this fixed-focus lens is well controlled and can meet the needs of wide-spectrum applications.

[0134] The above specific embodiments do not limit the scope of protection of this utility model. Those skilled in the art will appreciate that various modifications, combinations, sub-combinations, and substitutions may be made based on design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this utility model shall be included within the scope of protection of this utility model.

Claims

1. A fixed-focus lens, characterized in that: The optical system comprises a first lens having positive focal power, a second lens having positive focal power, a third lens having positive focal power, a fourth lens having negative focal power, a fifth lens having positive focal power, a sixth lens having negative focal power, a seventh lens having positive focal power, and an eighth lens having positive focal power, which are arranged in sequence from the object side to the image side along the optical axis; The fixed-focus lens further includes an aperture, and the aperture is located between the sixth lens and the seventh lens; The effective focal length of the fixed-focus lens at infinity and the total optical length of the fixed-focus lens satisfy: 1.112≤TTL / EFL≤1.622; Wherein, TTL represents the total optical length of the fixed-focus lens, and EFL represents the effective focal length of the fixed-focus lens at infinity.

2. The fixed-focus lens according to claim 1, wherein: The maximum image height of the fixed-focus lens and the back focal length of the fixed-focus lens satisfy: 0.732≤BFL / IH≤1.158; Wherein, BFL represents the back focal length of the fixed-focus lens; IH represents the maximum imaging height of the fixed-focus lens.

3. The fixed-focus lens according to claim 1, wherein: The refractive index of the seventh lens and the Abbe number of the eighth lens satisfy: Nd7≤1.95; Vd8≤95.00; Wherein, Nd7 represents the refractive index of the seventh lens, and Vd8 represents the Abbe number of the eighth lens.

4. The fixed-focus lens according to claim 1, wherein: The first lens and the second lens form a first cemented lens group with positive optical power. The focal length of the first lens and the combined focal length of the first cemented lens group satisfy: 0.795≤F1 / F101≤0.849; The focal length of the first cemented lens group and the effective focal length of the fixed-focus lens at infinity satisfy: 0.768≤F101 / EFL≤1.523; Wherein, F1 represents the focal length of the first lens, F101 represents the combined focal length of the first cemented lens group, and EFL represents the effective focal length of the fixed-focus lens at infinity.

5. The fixed-focus lens according to claim 1, wherein: The third lens, the sixth lens, and the eighth lens are all plastic aspherical lenses.

6. The fixed-focus lens according to claim 5, wherein: The focal length of the third lens, the focal length of the sixth lens, the focal length of the eighth lens, and the effective focal length of the fixed-focus lens at infinity satisfy: 5.513≤F3 / EFL≤11.151; -1.544≤F6 / EFL≤-0.725; 0.923≤F8 / EFL≤1.145; Wherein, F3, F6 and F8 represent the focal length of the third lens, the focal length of the sixth lens and the focal length of the eighth lens respectively, and EFL represents the effective focal length of the fixed-focus lens at infinity.

7. The fixed-focus lens according to claim 5, wherein: The first lens, the second lens, the fourth lens, the fifth lens and the seventh lens are all glass spherical lenses.

8. The fixed-focus lens according to claim 1, wherein: The maximum imaging height of the fixed-focus lens and the entrance pupil diameter of the fixed-focus lens satisfy: 0.402≤IH / EPD≤0.985; Wherein, IH represents the maximum imaging height of the fixed-focus lens; EPD represents the entrance pupil diameter of the fixed-focus lens.

9. The fixed-focus lens according to claim 1, wherein: The object-side surface of the first lens is convex, the object-side surface of the second lens is convex, and the image-side surface is concave, the object-side surface of the third lens is convex, and the image-side surface is concave, the object-side surface of the fourth lens is convex, the object-side surface of the fifth lens is convex, and the image-side surface is concave, the object-side surface of the sixth lens is concave, and the image-side surface is convex, the object-side surface of the seventh lens is convex, and the image-side surface is concave, and the object-side surface of the eighth lens is convex, and the image-side surface is concave.

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