Fixed-focus optical system and fixed-focus imaging device

Abstract

The invention discloses a fixed-focus optical system and a fixed-focus camera device, and relates to the technical field of optical systems.The fixed-focus optical system is provided with an object side and an image side which are correspondingly arranged in the light path direction; the fixed-focus optical system comprises a reflector, a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens and an image plane which are sequentially arranged from the object side to the image side in the light incidence direction, the focal power of the first lens is negative, the focal power of the second lens is negative, the focal power of the third lens is positive, and the focal power of the fourth lens is negative. The focal power of the fourth lens is negative, the focal power of the fifth lens is positive, the focal power of the sixth lens is positive, the focal power of the seventh lens is negative, one end face, facing the object side, of the reflector forms a reflecting face, and the reflecting face is used for changing the emergent direction of light. By means of the arrangement, the fixed focus optical system can have a picture close to 180 degrees, view finding of a 65-inch picture can be achieved under the distance of 60 mm, and meanwhile the effects of being small in size and low in cost are achieved.

Description

Technical Field

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

[0002] With the continuous growth of people's consumption demands, lenses have been developed for more and more usage scenarios. For extremely close-range shooting of a super-large picture, a fisheye lens is generally used. However, a fisheye lens often has a long structure, a large aperture, and a small picture angle, resulting in insufficient viewing experience, and there is also the problem of high cost. Summary of the Invention

[0003] The main object of the present invention is to provide a fixed-focus optical system and a fixed-focus imaging device, aiming to improve the problems of the existing fisheye lens, such as being too long in length, too large in aperture, having a small picture angle, and being too high in cost.

[0004] To achieve the above object, the fixed-focus optical system proposed by the present invention has an object side and an image side arranged correspondingly along the optical path direction. The fixed-focus optical system includes a reflecting mirror, a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, and an image plane arranged in sequence from the object side to the image side along the light incident direction. The optical power of the first lens is negative, the optical power of the second lens is negative, the optical power of the third lens is positive, the optical power of the fourth lens is negative, the optical power of the fifth lens is positive, the optical power of the sixth lens is positive, and the optical power of the seventh lens is negative. One end surface of the reflecting mirror facing the object side forms a reflecting surface, and the reflecting surface is used to change the light exit direction, changing the light incident from the object side to exit towards the image side. The fixed-focus optical system satisfies the following conditions: 1mm < f < 10mm, and 20mm < f1 < 10mm, and 10mm < f2 < 3mm, and 3mm < f3 < 10mm, and 10mm < f4 < 3mm, and 5mm < f5 < 15mm, and 1mm < f6 < 8mm, and 10mm < f7 < 1mm; Wherein, the focal length of the reflecting mirror is f, the focal length of the first lens is f1, the focal length of the second lens is f2, the focal length of the third lens is f3, the focal length of the fourth lens is f4, the focal length of the fifth lens is f5, the focal length of the sixth lens is f6, and the focal length of the seventh lens is f7.

[0005] In one embodiment, the object-side surface of the first lens is concave, and the image-side surface is also concave. The object-side surface of the second lens is concave, and the image-side surface is convex. 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 concave, and the image-side surface is convex. The object-side surface of the fifth lens is convex, and the image-side surface is also convex. 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 concave, and the image-side surface is also concave.

[0006] In one embodiment, the refractive index of the first lens is n1, where 1.60 ≤ n1 ≤ 1.70; The refractive index of the second lens is n2, where 1.50 ≤ n2 ≤ 1.60; The refractive index of the third lens is n3, where 1.50 ≤ n3 ≤ 1.60; The refractive index of the fourth lens is n4, where 1.60 ≤ n4 ≤ 1.70; The refractive index of the fifth lens is n5, where 1.45 ≤ n5 ≤ 1.60; The refractive index of the sixth lens is n6, where 1.50 ≤ n6 ≤ 1.60; The refractive index of the seventh lens is n7, where 1.60 ≤ n7 ≤ 1.70.

[0007] In one embodiment, the dispersion coefficient of the first lens is v1, where 20.0 ≤ v1 ≤ 30.0; The dispersion coefficient of the second lens is v2, 50.0≤v2≤60.0; The dispersion coefficient of the third lens is v3, where 50.0 ≤ v3 ≤ 60.0; The dispersion coefficient of the fourth lens is v4, where 20.0 ≤ v4 ≤ 30.0; The dispersion coefficient of the fifth lens is v5, 75.0≤v5≤95.0; The dispersion coefficient of the sixth lens is v6, 50.0≤v6≤60.0; The dispersion coefficient of the seventh lens is v7, where 20.0 ≤ v7 ≤ 30.0.

[0008] In one embodiment, the first lens, the second lens, the third lens, the fourth lens, the sixth lens, and the seventh lens are all configured as extended aspherical lenses.

[0009] In one embodiment, the diameter of the reflector is D0, wherein D0 ≤ 25 mm; and / or, The diameter of the first lens is D1, where D1 ≤ 10 mm; and / or, The diameter of the image plane is IC, where IC ≤ 2.5 mm; and / or, The effective focal length of the fixed-focus optical system is EFL, and the distance between the reflector and the image plane is TTL, wherein EFL / TTL≤0.0025.

[0010] In one embodiment, the fixed-focus optical system further includes an aperture stop disposed between the second lens and the third lens to adjust the aperture value of the fixed-focus optical system, wherein the aperture value of the fixed-focus optical system is Fno, and Fno≤2.7.

[0011] In one embodiment, the fixed-focus optical system further includes: A photosensitive chip, wherein the photosensitive chip is disposed on the image-side of the seventh lens, and the object-side end face of the photosensitive chip forms the image plane; and, A protective glass is disposed between the seventh lens and the photosensitive chip.

[0012] In one embodiment, the reflective surface is configured as either an extended aspherical surface or a freeform surface.

[0013] The present invention also proposes a fixed-focus camera device, including the aforementioned fixed-focus optical system.

[0014] In the technical solution of this invention, the fixed-focus optical system is composed of the reflector and seven lenses. By setting the optical power of the first lens to negative, the fixed-focus optical system can effectively collect light, thereby increasing the field of view and correcting astigmatism and field curvature. When the fixed-focus optical system captures an image, the light beam first illuminates the reflective surface of the reflector. At this time, the light beam is reflected on the reflective surface to change the direction of the light path, so that the light beam can pass through the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, and the seventh lens in sequence. Through the cooperation of the seven lenses, the light beam is converged and corrected, thereby forming a clear image on the image plane. This configuration, through the placement of the reflector, allows for the alteration of the light beam's propagation direction, thereby shortening the overall length of the fixed-focus optical system's lens. Furthermore, by adjusting the optical power of the first lens, the system's light intake is ensured while avoiding an excessively large aperture that would make the fixed-focus optical system too bulky. Ultimately, by coordinating the optical power and focal length of the seven lenses, the fixed-focus optical system achieves compactness and lightweight design. The rational arrangement of the seven lenses also improves the imaging quality of the fixed-focus optical system, resulting in a near 180° field of view and the ability to frame a 65-inch image from a distance of 60mm, while simultaneously achieving a small size and low cost. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0016] Figure 1 This is a schematic diagram of the structure of an embodiment of the fixed-focus optical system provided by the present invention; Figure 2 for Figure 1 Schematic diagram of the transverse chromatic aberration curve of a fixed-focus optical system; Figure 3 for Figure 1 Schematic diagram of the SPOT point of a fixed-focus optical system; Figure 4 for Figure 1 A diagram showing the overall structure of the fixed-focus optical system and the viewfinder.

[0017] Explanation of icon numbers: 100. Fixed-focus optical system; 1. First lens; 2. Second lens; 3. Third lens; 4. Fourth lens; 5. Fifth lens; 6. Sixth lens; 7. Seventh lens; 8. Mirror; 9. Image plane; 10. Aperture stop; 11. Image sensor; 12. Protective glass.

[0018] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0020] It should be noted that if the embodiments of the present invention involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a specific posture. If the specific posture changes, the directional indicators will also change accordingly.

[0021] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the use of "and / or" or "and / or" throughout the text includes three parallel solutions. For example, "A and / or B" includes solution A, solution B, or a solution where both A and B are satisfied simultaneously. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0022] This invention proposes a fixed-focus optical system, which aims to improve the problems of existing fisheye lenses being too long, too large in diameter, and having a small field of view and high cost.

[0023] Please see Figure 1 and Figure 4, in an embodiment of the present invention, the fixed-focus optical system 100 has an object side and an image side arranged correspondingly along the optical path direction. The fixed-focus optical system 100 includes a reflector 8, a first lens 1, a second lens 2, a third lens 3, a fourth lens 4, a fifth lens 5, a sixth lens 6, a seventh lens 7, and an image plane 9 arranged in sequence from the object side to the image side along the light incident direction. The optical power of the first lens 1 is negative, the optical power of the second lens 2 is negative, the optical power of the third lens 3 is positive, the optical power of the fourth lens 4 is negative, the optical power of the fifth lens 5 is positive, the optical power of the sixth lens 6 is positive, and the optical power of the seventh lens 7 is negative. One end face of the reflector 8 facing the object side forms a reflecting surface, and the reflecting surface is used to change the outgoing direction of the light, changing the light incident from the object side to be outgoing towards the image side. The fixed-focus optical system 100 satisfies the following conditions: 1 mm < f < 10 mm, and 20 mm < f1 < 10 mm, and 10 mm < f2 < 3 mm, and 3 mm < f3 < 10 mm, and 10 mm < f4 < 3 mm, and 5 mm < f5 < 15 mm, and 1 mm < f6 < 8 mm, and 10 mm < f7 < 1 mm, where the focal length of the reflector 8 is f, the focal length of the first lens 1 is f1, the focal length of the second lens 2 is f2, the focal length of the third lens 3 is f3, the focal length of the fourth lens 4 is f4, the focal length of the fifth lens 5 is f5, the focal length of the sixth lens 6 is f6, and the focal length of the seventh lens 7 is f7.

[0024] In the technical solution of the present invention, the fixed-focus optical system 100 is composed of the reflector 8 and seven lenses. By setting the optical power of the first lens 1 to negative, the fixed-focus optical system 100 can collect light, thereby effectively increasing the field of view of the fixed-focus optical system 100 and correcting astigmatism and field curvature. When the fixed-focus optical system 100 captures an image, the light beam first illuminates the reflective surface of the reflector 8. At this time, the light beam is reflected on the reflective surface to change the direction of the light beam, so that the light beam can pass through the first lens 1, the second lens 2, the third lens 3, the fourth lens 4, the fifth lens 5, the sixth lens 6 and the seventh lens 7 in sequence. Through the cooperation of the seven lenses, the light beam is converged and corrected, thereby forming a clear image on the image plane 9. This configuration, through the placement of the reflector 8, allows for the alteration of the light beam's transmission direction, thereby shortening the overall length of the lens in the fixed-focus optical system 100. Furthermore, by adjusting the optical power of the first lens 1, the system ensures sufficient light intake while avoiding an excessively large aperture that would make the fixed-focus optical system 100 too bulky. Ultimately, by coordinating the optical power and focal length of the seven lenses, the fixed-focus optical system 100 achieves a compact and lightweight design. The rational arrangement of the seven lenses also improves the image quality of the fixed-focus optical system 100, resulting in a near 180° field of view and the ability to frame a 65-inch image from a distance of 60mm, while simultaneously achieving a small size and low cost.

[0025] First, this invention does not limit the specific surface shapes of the first lens 1, the second lens 2, the third lens 3, the fourth lens 4, the fifth lens 5, the sixth lens 6, and the seventh lens 7. In this invention, the specific surface shapes of the object side and the image side of the first lens 1, the second lens 2, the third lens 3, the fourth lens 4, the fifth lens 5, the sixth lens 6, and the seventh lens 7 can be selected according to requirements. In the actual setting process, it is only necessary to ensure that the matching of the object side surface shape and the image side surface shape of each lens can correspond to the optical power of each lens. This invention does not impose any restrictions on this.

[0026] For example, in one embodiment of the present invention, the object-side surface of the first lens 1 is concave, the image-side surface is concave, and the optical power of the first lens 1 is negative; the object-side surface of the second lens 2 is concave, the image-side surface is convex, and the optical power of the second lens 2 is negative; the object-side surface of the third lens 3 is convex, the image-side surface is concave, and the optical power of the third lens 3 is positive; the object-side surface of the fourth lens 4 is concave, the image-side surface is convex, and the optical power of the fourth lens 4 is negative; the object-side surface of the fifth lens 5 is convex, the image-side surface is convex, and the optical power of the fifth lens 5 is positive; the object-side surface of the sixth lens 6 is concave, the image-side surface is convex, and the optical power of the sixth lens 6 is positive; and the object-side surface of the seventh lens 7 is concave, the image-side surface is concave, and the optical power of the seventh lens 7 is negative. This configuration, through the arrangement of the surface shapes of the first lens 1, the second lens 2, the third lens 3, the fourth lens 4, the fifth lens 5, the sixth lens 6, and the seventh lens 7, ensures a good working relationship between the seven lenses, thereby guaranteeing the imaging quality of the fixed-focus optical system 100.

[0027] Of course, the present invention does not limit the specific values ​​of the focal lengths of the first lens 1, the second lens 2, the third lens 3, the fourth lens 4, the fifth lens 5, the sixth lens 6, and the seventh lens 7. In the present invention, the focal lengths of the first lens 1, the second lens 2, the third lens 3, the fourth lens 4, the fifth lens 5, the sixth lens 6, and the seventh lens 7 can be selected according to the actual situation, as long as the specific values ​​of the focal lengths of each lens are within the corresponding value range.

[0028] Similarly, the present invention does not limit the specific focal length value of the reflector 8. In the present invention, the specific focal length value of the reflector 8 can be set to any value within its range. In actual setting, it can be selected according to the requirements.

[0029] It should also be noted that, to avoid the fixed-focus optical system 100 having an excessively large aperture and thus becoming too bulky, the diameter of the reflector 8 needs to be limited in this invention. In one embodiment of this invention, the diameter of the reflector 8 is D0, where D0 ≤ 25mm. This setting, by limiting the maximum diameter of the reflector 8, limits the aperture of the fixed-focus optical system 100, thereby ensuring the miniaturization of the fixed-focus optical system 100.

[0030] It is understood that the present invention does not limit the specific value of the diameter of the reflector 8. In the present invention, the diameter of the reflector 8 can be set to any value within its range, as long as the reflector 8 can reflect the light beam. In actual setting, it can be selected according to the requirements.

[0031] Furthermore, in this invention, to reduce the manufacturing cost of the fixed-focus optical system 100, some lenses can be configured as aspherical lenses. Aspherical lenses are typically made of plastic, which is less expensive than glass. This effectively reduces the overall manufacturing cost of the fixed-focus optical system 100 while maintaining image quality. Simultaneously, plastic materials possess a degree of flexibility, making them less prone to damage from minor external impacts compared to glass lenses, thus improving the durability of the fixed-focus optical system 100.

[0032] Of course, the present invention does not limit the specific number of lenses to be set as aspherical lenses; the number of lenses can be selected according to the actual needs during the actual setting.

[0033] In one embodiment of the present invention, the first lens 1, the second lens 2, the third lens 3, the fourth lens 4, the sixth lens 6, and the seventh lens 7 are all configured as aspherical lenses. Specifically, the first lens 1, the second lens 2, the third lens 3, the fourth lens 4, the sixth lens 6, and the seventh lens 7 are all configured as extended aspherical lenses.

[0034] In this embodiment, the fifth lens 5 is set as a spherical lens. By using a spherical lens, the cost of the fixed-focus optical system 100 can be reduced while ensuring the imaging quality and reliability of the fixed-focus optical system 100, thereby reducing assembly sensitivity and improving the yield of finished products.

[0035] Furthermore, to avoid an excessively large aperture in the fixed-focus optical system 100, the diameter of the first lens 1 needs to be further limited. In one embodiment of the invention, the diameter of the first lens 1 is D1, where D1 ≤ 10 mm. This limitation restricts the aperture of the fixed-focus optical system 100, thereby preventing an excessively large aperture and meeting the installation space requirements of the final product.

[0036] Of course, the present invention does not limit the specific surface shape of the reflecting surface of the reflector 8. In one embodiment of the present invention, the reflecting surface can be set as a plane; in another embodiment of the present invention, the reflecting surface can be set as a sphere; in yet another embodiment of the present invention, the reflecting surface can also be set as an extended aspherical surface; and in other embodiments of the present invention, the reflecting surface can also be set as a free-form surface or other surface shape. In actual setting, it can be selected according to the requirements.

[0037] Specifically, in this embodiment, the reflective surface is configured as either an extended aspherical surface or a freeform surface.

[0038] Furthermore, in one embodiment of the present invention, the refractive index of the first lens 1 is n1, 1.60≤n1≤1.70; the refractive index of the second lens 2 is n2, 1.50≤n2≤1.60; the refractive index of the third lens 3 is n3, 1.50≤n3≤1.60; the refractive index of the fourth lens 4 is n4, 1.60≤n4≤1.70; the refractive index of the fifth lens 5 is n5, 1.45≤n5≤1.60; the refractive index of the sixth lens 6 is n6, 1.50≤n6≤1.60; and the refractive index of the seventh lens 7 is n7, 1.60≤n7≤1.70.

[0039] Of course, in this invention, the specific values ​​of the refractive index of the first lens 1, the second lens 2, the third lens 3, the fourth lens 4, the fifth lens 5, the sixth lens 6, and the seventh lens 7 are not limited. The refractive indices of the first lens 1, the second lens 2, the third lens 3, the fourth lens 4, the fifth lens 5, the sixth lens 6, and the seventh lens 7 can also be selected according to requirements, as long as the specific value of the refractive index of each lens is within the corresponding value range.

[0040] For example, in one embodiment of the present invention, the refractive index of the first lens 1 can be set to 1.6397, the refractive index of the second lens 2 can be set to 1.535, the refractive index of the third lens 3 can be set to 1.535, the refractive index of the fourth lens 4 can be set to 1.6397, the refractive index of the fifth lens 5 can be set to 1.497, the refractive index of the sixth lens 6 can be set to 1.535, and the refractive index of the seventh lens 7 can be set to 1.6397. With this configuration, in this embodiment, the specific values ​​of the refractive indices of the first lens 1, the second lens 2, the third lens 3, the fourth lens 4, the fifth lens 5, the sixth lens 6, and the seventh lens 7 are all within their respective numerical ranges, ensuring stable imaging of the fixed-focus optical system 100.

[0041] Similarly, in this invention, the dispersion coefficient of the first lens 1 is v1, 20.0≤v1≤30.0; the dispersion coefficient of the second lens 2 is v2, 50.0≤v2≤60.0; the dispersion coefficient of the third lens 3 is v3, 50.0≤v3≤60.0; the dispersion coefficient of the fourth lens 4 is v4, 20.0≤v4≤30.0; the dispersion coefficient of the fifth lens 5 is v5, 75.0≤v5≤95.0; the dispersion coefficient of the sixth lens 6 is v6, 50.0≤v6≤60.0; and the dispersion coefficient of the seventh lens 7 is v7, 20.0≤v7≤30.0.

[0042] This invention also does not limit the specific values ​​of the dispersion coefficients of the first lens 1, the second lens 2, the third lens 3, the fourth lens 4, the fifth lens 5, the sixth lens 6, and the seventh lens 7. The dispersion coefficients of the first lens 1, the second lens 2, the third lens 3, the fourth lens 4, the fifth lens 5, the sixth lens 6, and the seventh lens 7 can also be selected according to requirements, as long as the specific values ​​of the dispersion coefficients of each lens are within the corresponding value range.

[0043] In a specific embodiment of the present invention, the dispersion coefficient of the first lens 1 can be set to 23.503, the dispersion coefficient of the second lens 2 can be set to 55.711, the dispersion coefficient of the third lens 3 can be set to 55.711, the dispersion coefficient of the fourth lens 4 can be set to 23.503, the dispersion coefficient of the fifth lens 5 can be set to 81.613, the dispersion coefficient of the sixth lens 6 can be set to 55.711, and the dispersion coefficient of the seventh lens 7 can be set to 23.503. It is also understood that in this embodiment, the dispersion coefficients of the first lens 1, the second lens 2, the third lens 3, the fourth lens 4, the fifth lens 5, the sixth lens 6, and the seventh lens 7 are all within their respective numerical ranges, thereby ensuring stable imaging of the fixed-focus optical system 100.

[0044] Furthermore, this invention does not limit the aperture value of the new fixed-focus optical system. In one embodiment, the fixed-focus optical system 100 further includes an aperture stop 10, which is disposed between the second lens 2 and the third lens 3 to adjust the aperture value of the fixed-focus optical system 100. The aperture value of the fixed-focus optical system 100 is Fno, where Fno ≤ 2.7. This configuration enables the fixed-focus optical system 100 to have a large light throughput and high image brightness, allowing for clear imaging even in low light conditions. Simultaneously, the aperture stop 10 further reduces stray light interference with the fixed-focus optical system 100, thereby further improving the imaging quality of the fixed-focus optical system 100.

[0045] It should also be noted that, in this invention, the volume of the fixed-focus optical system 100 can be further controlled. In one embodiment of this invention, the diameter of the image plane 9 is IC, where IC ≤ 2.5 mm.

[0046] In another embodiment of the present invention, the effective focal length of the fixed-focus optical system 100 is EFL, and the distance between the reflector 8 and the image plane 9 is TTL, wherein EFL / TTL≤0.0025.

[0047] In another embodiment of the present invention, the fixed-focus optical system 100 further includes a photosensitive chip 11 and a protective glass 12. The photosensitive chip 11 is disposed on the image-side of the seventh lens 7, and the object-side end face of the photosensitive chip 11 forms the image plane 9. The protective glass 12 is disposed between the seventh lens 7 and the photosensitive chip 11. The protective glass 12 effectively protects the photosensitive chip 11 from damage caused by external factors such as dust and moisture, thereby extending the service life of the fixed-focus optical system 100.

[0048] It is understandable that the protective glass 12 needs to be made of a material with good optical properties, so as to reduce the impact on image quality while ensuring light transmittance.

[0049] In one specific embodiment of the present invention, the focal length of the fixed-focus optical system 100 is f = 0.104468 mm.

[0050] In this embodiment, the surface type, radius of curvature, thickness, material refractive index, and Abbe number of the multiple lenses are shown in Table 1 below: Table 1

[0051] In this application, since the first lens 1, the second lens 2, the third lens 3, the fourth lens 4, the sixth lens 6, and the seventh lens 7 are all configured as extended aspherical lenses, the surface shape of the extended aspherical lens satisfies the following conditions:

[0052] Where Z represents the distance of the surface from its vertex along the optical axis, c is the curvature of the vertex, y is the distance from the optical axis to the surface, and k is the conic coefficient (when k is less than...). When k equals 1, the surface curve is a hyperbola. When k is 1, it is a parabola; when the coefficient k is between (When the value is between 1 and 0, it is an ellipse; when the k coefficient is equal to 0, it is a circle; when the k coefficient is greater than 0, it is an oval.) A, B, C, D, E, F, G, H, and I represent the fourth, sixth, eighth, tenth, twelfth, fourteenth, sixteenth, eighteenth, and twentieth order aspherical coefficients, respectively. The shape and size of the aspherical surfaces on the object side and image side of the lens can be set by using the above parameters.

[0053] One design value for the aspheric coefficient in this embodiment is shown in Table 2 below: Table 2

[0054] It should be noted that Table 2 is a design value of the aspherical coefficient of the lens in the fixed-focus optical system 100 described in this embodiment. The specific value of the aspherical coefficient design can be adjusted according to the needs of the product, and the present invention does not limit it.

[0055] Please see Figure 2 , Figure 2 A schematic diagram of the chromatic aberration curve of the fixed-focus optical system 100 provided by the present invention.

[0056] Please see Figure 3 , Figure 3 This is a schematic diagram of the SPOT point of the fixed-focus optical system 100 provided by the present invention.

[0057] The present invention also proposes a fixed-focus camera device, which includes a fixed-focus optical system. The specific structure of the fixed-focus optical system is as described in the above embodiments. Since the fixed-focus camera device adopts all the technical solutions of all the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be described in detail here.

[0058] The above description is merely an exemplary embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention specification and drawings under the technical concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A fixed focus optical system characterized in that, The fixed focus optical system has an object side and an image side corresponding to the arrangement of the optical path, and comprises, in sequence from the object side to the image side along the direction of light incidence, a mirror, a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, and an image plane, the first lens has a negative refractive power, the second lens has a negative refractive power, the third lens has a positive refractive power, the fourth lens has a negative refractive power, the fifth lens has a positive refractive power, the sixth lens has a positive refractive power, and the seventh lens has a negative refractive power, an end surface of the mirror towards the object side forms a reflecting surface, the reflecting surface is used to change the direction of light emission, and the light incident from the object side is changed to be emitted towards the image side, and the fixed focus optical system satisfies the following conditions: 1 mm < f < 10 mm, and 20 mm < f1 10 mm, and 10 mm < f2 3 mm, and 3 mm < f3 < 10 mm, and 10 mm < f4 3 mm, and 5 mm < f5 < 15 mm, and 1 mm < f6 < 8 mm, and 10 mm < f7 1 mm; Wherein, the focal length of the mirror is f, the focal length of the first lens is f1, the focal length of the second lens is f2, the focal length of the third lens is f3, the focal length of the fourth lens is f4, the focal length of the fifth lens is f5, the focal length of the sixth lens is f6, and the focal length of the seventh lens is f7.

2. The fixed focus optical system of claim 1, wherein The object side surface of the first lens is a concave surface, and the image side surface is a concave surface; The object side surface of the second lens is a concave surface, and the image side surface is a convex surface; The object side surface of the third lens is a convex surface, and the image side surface is a concave surface; The object side surface of the fourth lens is a concave surface, and the image side surface is a convex surface; The object side surface of the fifth lens is a convex surface, and the image side surface is a convex surface; The object side surface of the sixth lens is a concave surface, and the image side surface is a convex surface; The object side surface of the seventh lens is a concave surface, and the image side surface is a concave surface.

3. The fixed focus optical system of claim 1, wherein The refractive index of the first lens is n1, and 1.60≤n1≤1.70; The refractive index of the second lens is n2, and 1.50≤n2≤1.60; The refractive index of the third lens is n3, and 1.50≤n3≤1.60; The refractive index of the fourth lens is n4, and 1.60≤n4≤1.70; The refractive index of the fifth lens is n5, and 1.45≤n5≤1.60; The refractive index of the sixth lens is n6, and 1.50≤n6≤1.60; The refractive index of the seventh lens is n7, and 1.60≤n7≤1.

70.

4. The fixed focus optical system of claim 1, wherein The dispersion coefficient of the first lens is v1, and 20.0≤v1≤30.0; The dispersion coefficient of the second lens is v2, and 50.0≤v2≤60.0; The dispersion coefficient of the third lens is v3, and 50.0≤v3≤60.0; The dispersion coefficient of the fourth lens is v4, and 20.0≤v4≤30.0; The dispersion coefficient of the fifth lens is v5, and 75.0≤v5≤95.0; The dispersion coefficient of the sixth lens is v6, and 50.0≤v6≤60.0; The dispersion coefficient of the seventh lens is v7, and 20.0≤v7≤30.

0.

5. The fixed focus optical system of claim 1, wherein The first lens, the second lens, the third lens, the fourth lens, the sixth lens, and the seventh lens are all extended aspherical lenses.

6. The fixed focus optical system of claim 1, wherein The diameter of the mirror is D0, wherein D0≤25mm; and / or, The diameter of the first lens is D1, wherein D1≤10mm; and / or, The diameter of the image plane is IC, where IC ≤ 2.5 mm; and / or, The effective focal length of the fixed-focus optical system is EFL, and the distance between the reflector and the image plane is TTL, wherein EFL / TTL≤0.0025.

7. The fixed focus optical system of claim 1, wherein The fixed-focus optical system further includes an aperture stop, which is disposed between the second lens and the third lens to adjust the aperture value of the fixed-focus optical system. The aperture value of the fixed-focus optical system is Fno, where Fno≤2.

7.

8. The fixed focus optical system of claim 1, wherein The fixed-focus optical system also includes: A photosensitive chip, wherein the photosensitive chip is disposed on the image-side of the seventh lens, and the object-side end face of the photosensitive chip forms the image plane; and, A protective glass is disposed between the seventh lens and the photosensitive chip.

9. The fixed focus optical system of claim 1, wherein The reflective surface is configured as either an extended aspherical surface or a freeform surface.

10. An afocal camera characterized by, Includes the fixed-focus optical system as described in any one of claims 1 to 9.

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