Compact wide-angle camera lens and imaging device

Abstract

The application provides a compact wide-angle camera lens and an imaging device, which comprises, from an object side to an image side, a first lens with negative refractive power and a concave image side, a second lens with positive refractive power, a diaphragm, a third lens with positive refractive power, a fourth lens with positive refractive power, a fifth lens with negative refractive power, a bonded lens group composed of a sixth lens and a seventh lens, and an eighth lens with positive refractive power. The fifth lens is a non-spherical plastic lens, and the other lenses are glass lenses. The application uses a specific refractive power arrangement and a glass-plastic hybrid structure to locally compensate for the surface characteristics of the non-spherical plastic lens, reduce the system distortion under a large field of view, and limit the total optical length and reduce the volume.

Description

Technical Field

[0001] This invention relates to the field of optical imaging technology, and more specifically to a compact wide-angle camera lens and imaging device. Background Technology

[0002] In modern photography and specific shooting scenarios, the requirements for field of view and portability of equipment are constantly increasing. However, conventional camera lenses typically have a limited field of view, generally less than 50°, making it difficult to meet the needs of shooting at a wide angle. To further expand the field of view of a lens, it is usually necessary to increase the number or size of optical elements, which leads to a significant increase in the overall optical length of the lens. This large structure not only reduces the portability of the equipment but also makes it difficult to effectively control optical distortion and chromatic aberration while achieving an ultra-wide field of view. Summary of the Invention

[0003] In view of the aforementioned problems, this application is made to provide a compact wide-angle camera lens and imaging device that overcomes or at least partially solves the aforementioned problems, comprising: A compact wide-angle camera lens, comprising, from the object side to the image side: The first lens has negative optical power and the image side of the first lens is concave. A second lens, the second lens having positive optical power; Aperture; A third lens, wherein the third lens has positive optical power; A fourth lens, wherein the fourth lens has positive optical power; The fifth lens has a negative optical power; A bonded lens assembly, wherein the bonded lens assembly is formed by bonding together a sixth lens and a seventh lens having optical power; The eighth lens has positive optical power; The fifth lens is an aspherical plastic lens; the first lens, the second lens, the third lens, the fourth lens, the sixth lens, the seventh lens, and the eighth lens are all glass lenses.

[0004] According to one embodiment of the present invention, the first lens, the second lens, and the third lens are all convex-concave lenses; the fourth lens and the eighth lens are both biconvex lenses; and the fifth lens is a concave-convex lens.

[0005] According to one embodiment of the present invention, the object-side surface and image-side surface of the first lens, the second lens, the third lens, the fourth lens, the sixth lens, the seventh lens and the eighth lens are all spherical.

[0006] According to one embodiment of the present invention, the focal length of the first lens is f1, the focal length of the second lens is f2, and the focal length of the third lens is f3, wherein |f1| < 23 mm; |f2| < 20 mm; and |f3| > 23 mm.

[0007] According to one embodiment of the present invention, the focal length of the fourth lens is f4, the focal length of the fifth lens is f5, the focal length of the bonded lens group is f6 / 7, and the focal length of the eighth lens is f8, wherein |f4| < 20mm; |f5| < 20mm; |f6 / 7| > 90mm; and |f8| > 40mm.

[0008] According to one embodiment of the present invention, the total optical length of the compact wide-angle camera lens is TTL, and the optical back focal length of the compact wide-angle camera lens is BFL, wherein TTL≤35mm; BFL≥12mm.

[0009] According to one embodiment of the present invention, the compact wide-angle camera lens is further provided with a protective glass and a photosensitive chip in sequence from the object side to the image side after the eighth lens; the aperture of the compact wide-angle camera lens corresponds to an FNO of 5.6.

[0010] According to one embodiment of the present invention, the field of view of the compact wide-angle camera lens is not less than 100°; the image plane diameter of the photosensitive chip is not less than 43.2 mm.

[0011] According to one embodiment of the present invention, the aspherical surface shape of the fifth lens satisfies the following conic quadratic equation:

[0012] Where z is the sag of the aspherical surface along the optical axis at a height of y, c is the curvature of the vertex of the aspherical surface, y is the radial coordinate, and k is the conic conic coefficient. to These are the higher-order aspheric coefficients from the 4th to the 16th order.

[0013] An imaging device comprising a compact wide-angle camera lens as described above.

[0014] This application has the following advantages: In the embodiments of this application, a combination of lenses with specific optical power arranged sequentially from the object side to the image side, with an aperture stop positioned between the second and third lenses, is used to adjust large-angle light rays so that the light rays enter the aperture stop smoothly. At the same time, a combination of an aspherical plastic lens as the fifth lens and glass lenses as the remaining lenses is used. While limiting the total optical length, the aspherical feature reduces system distortion. In conjunction with the bonded lens group and the positive optical power eighth lens on the image side, chromatic aberration and aberration correction are completed. The camera lens of this invention overcomes the shortcomings of the prior art in that it is difficult to balance a large field of view with a small volume, and achieves the effect of expanding the field of view, reducing the volume, and ensuring image quality. Attached Figure Description

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

[0016] Figure 1 A schematic diagram of the optical structure of a compact wide-angle camera lens provided in an embodiment of this application; Figure 2 A schematic diagram of ray tracing for a compact wide-angle camera lens provided in an embodiment of this application; Figure 3 An optical modulation transfer function (MTF) curve of a compact wide-angle camera lens provided in an embodiment of this application; Figure 4 Field curvature and distortion diagram of a compact wide-angle camera lens provided in an embodiment of this application.

[0017] Figure label: 10. First lens; 20. Second lens; ST, aperture stop; 30. Third lens; 40. Fourth lens; 50. Fifth lens; 60. Sixth lens; 70. Seventh lens; 80. Eighth lens; 90. Protective glass; 100. Photosensitive chip. Detailed Implementation

[0018] To make the objectives, features, and advantages of this application more apparent and understandable, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0019] The inventors, through analysis of existing technologies, discovered that conventional designs typically employ a stacked all-glass lens structure to achieve wide-angle imaging. While this can correct chromatic aberration by increasing the thickness and number of lenses, it directly results in an inability to effectively compress the overall optical length, making it difficult to meet the miniaturization requirements of current devices. Furthermore, in traditional all-glass lens structures, attempting to correct distortion caused by ultra-wide-angle imaging solely by increasing the number of spherical lenses often leads to increased sensitivity between lenses, and the distortion correction effect is not ideal. Based on this, the inventors proposed using the surface features of aspherical plastic lenses to correct distortion, thereby reducing the size of the optical system while controlling large-angle imaging distortion.

[0020] Reference Figures 1 to 2 This illustration shows a compact wide-angle camera lens provided in an embodiment of the present application, which includes, from the object side to the image side, a first lens 10, a second lens 20, an aperture ST, a third lens 30, a fourth lens 40, a fifth lens 50, a bonding lens group, and an eighth lens 80.

[0021] Specifically, the first lens 10 has negative optical power, and its image-side surface is concave. The second lens 20 has positive optical power and is disposed on the image-side of the first lens 10. An aperture stop ST is disposed between the image-side of the second lens 20 and the object-side of the third lens 30. The wide-angle incident beam from the object side undergoes divergence and refraction path adjustment via the negative optical power of the first lens 10 and its concave image-side structure, and then enters the second lens 20 with positive optical power for initial convergence.

[0022] Both the third lens 30 and the fourth lens 40 have positive optical power and are sequentially arranged along the principal optical axis on the image side of the aperture ST. Light rays passing through the aperture ST sequentially pass through the third lens 30 and the fourth lens 40, and the positive optical power of both lenses is used to continuously converge the light and adjust the chromatic aberration.

[0023] The fifth lens 50 has negative optical power and is located on the image side of the fourth lens 40. In this application, the fifth lens 50 is an aspherical plastic lens, while the first lens 10, second lens 20, third lens 30, and fourth lens 40 are all glass lenses. After the light beam enters the fifth lens 50, it is regularly deflected by the combined effect of its negative optical power and aspherical surface shape. The distortion of the optical system is compensated by the aspherical surface shape characteristics.

[0024] A bonded lens assembly is disposed on the image side of the fifth lens 50. This bonded lens assembly is formed by bonding together a sixth lens 60 and a seventh lens 70, both having optical power. An eighth lens 80, having positive optical power, is disposed on the image side of the bonded lens assembly. In this application, the sixth lens 60, the seventh lens 70, and the eighth lens 80 are all glass lenses. Light rays emitted from the fifth lens 50 enter the bonded lens assembly. The residual chromatic aberration in the light path is further controlled by the light-transmitting interface between the sixth lens 60 and the seventh lens 70, as well as the optical power. Finally, the light is converged at the end by the eighth lens 80, which has positive optical power, and projected onto the image plane.

[0025] In the embodiments of this application, a combination of specific optical power lenses arranged sequentially from the object side to the image side is used, and the aperture stop ST is set between the second lens 20 and the third lens 30 to adjust large-angle light so that the light enters the aperture stop ST smoothly. At the same time, a combination of a fifth lens 50 being an aspherical plastic lens and the remaining lenses being glass lenses is used. While limiting the total optical length, the aspherical feature reduces system distortion. In conjunction with the bonded lens group and the positive optical power eighth lens 80 on the image side, chromatic aberration and aberration correction are completed. The camera lens of this invention overcomes the shortcomings of the prior art in that it is difficult to balance a large field of view with a small volume, and achieves the effect of expanding the field of view, reducing the volume, and ensuring image quality.

[0026] In one embodiment of the present invention, the first lens 10, the second lens 20, and the third lens 30 are all convex-concave lenses; the fourth lens 40 and the eighth lens 80 are both biconvex lenses; and the fifth lens 50 is a concave-convex lens. Preferably, the object-side surface and image-side surface of the first lens 10, the second lens 20, the third lens 30, the fourth lens 40, the sixth lens 60, the seventh lens 70, and the eighth lens 80 are all spherical.

[0027] In the beam transmission path, three consecutively arranged convex and concave lenses (first lens 10, second lens 20, and third lens 30) can smoothly deflect the edge light rays with a large field of view, guiding the large-angle incident beam into the lens interior step by step. The object-side and image-side surfaces of the fourth lens 40 and the eighth lens 80 both convex outwards, providing the required positive optical power through a biconvex shape, thereby achieving light convergence. In other examples, the object-side surface of the fifth lens 50 is concave, and the image-side surface is configured as convex; it is integrally molded from optical plastic using an injection molding process to form a meniscus shape.

[0028] In this embodiment, the above-mentioned lens surface combination is adopted. By combining the continuous folding of the front convex and concave lens with the converging of the rear biconvex lens, the incident angle of light at the optical interface of each lens is reduced, thus limiting the excessive accumulation of aberrations. At the same time, the concave and convex meniscus aspherical structure of the fifth lens 50 is used to perform local path compensation of light, further reducing the optical distortion of the system under ultra-large field of view.

[0029] In one embodiment of the present invention, the focal length of the first lens 10 is f1, the focal length of the second lens 20 is f2, and the focal length of the third lens 30 is f3, wherein |f1| < 23 mm; |f2| < 20 mm; and |f3| > 23 mm.

[0030] In this embodiment, |f1| < 23mm, which gives the first lens 10, with its negative optical power, a high light divergence capability, enabling initial divergence and field-of-view compression of large-angle edge-incident beams. The second lens 20, with |f2| < 20mm, utilizes its strong positive optical power to quickly converge the diverged light. Together, they complete the initial deflection of large-angle beams and smoothly guide them into subsequent structures. Furthermore, |f3| > 23mm, which results in a relatively even distribution of positive optical power in the third lens 30, preventing excessive convergence of the beam after passing through the aperture ST.

[0031] By adopting the above-mentioned focal length parameter range, the light deflection load of the front lens group is distributed, ensuring that the lens has a large field of view capture capability, avoiding higher-order aberrations caused by excessive local focal length, and limiting the thickness of the front lens.

[0032] In one embodiment of the present invention, the focal length of the fourth lens 40 is f4, the focal length of the fifth lens 50 is f5, the focal length of the bonded lens group is f6 / 7, and the focal length of the eighth lens 80 is f8, wherein |f4| < 20mm; |f5| < 20mm; |f6 / 7| > 90mm; and |f8| > 40mm.

[0033] In this embodiment, |f4| < 20mm, ensuring that the fourth lens 40 maintains a high light-converging ability. In the fifth lens 50, |f5| < 20mm, its strong negative optical power applies a reverse divergence effect to the converging beam. The two lenses form an alternating combination of strong positive and negative optical power, canceling out higher-order spherical aberrations and astigmatism in the system. |f6 / 7| > 90mm, making the overall optical power of the bonded lens group approach a smooth curve. It locally compensates for axial chromatic aberration through the cemented interface between the sixth lens 60 and the seventh lens 70, preventing excessive beam deflection. Finally, |f8| > 40mm, allowing the eighth lens 80 to guide light with a gentler refractive index, projecting it onto the image plane at a set angle. Therefore, by combining the aberration antagonism of the high-power lens with the chromatic aberration compensation of the low-power bonded lens group, the optical power distribution in the rear half of the lens can be made more balanced, and the incident angle deviation when the light is projected at the edge of the field of view can be reduced while controlling the total optical length.

[0034] It should be noted that after passing through the aperture ST, the air gap between the third lens 30 and the fourth lens 40 is extremely small, forming a near-bonded composite lens in terms of optical structure. This structure can effectively coordinate the positive optical power of both lenses to continuously and smoothly converge the light beam, thereby further correcting the chromatic aberration of the system.

[0035] In some embodiments of the present invention, the total optical length of the compact wide-angle camera lens is TTL, and the optical back focal length of the compact wide-angle camera lens is BFL, wherein TTL≤35mm; BFL≥12mm.

[0036] TTL defines the physical distance along the principal optical axis from the vertex of the object side of the first lens 10 to the final image plane. A TTL ≤ 35mm results in a short axis distance lens. BFL defines the distance from the vertex of the image side of the eighth lens 80 to the image plane; a BFL ≥ 12mm provides a physical assembly gap for the rear protective glass or photosensitive components. This parameter range, while ensuring a wide field of view transmission path, limits the overall axial dimensions of the lens structure, reducing lens size and weight, and improving portability.

[0037] In some embodiments of the present invention, a protective glass 90 and a photosensitive chip 100 are sequentially arranged after the eighth lens 80 from the object side to the image side of the compact wide-angle camera lens. The aperture of this compact wide-angle camera lens corresponds to an FNO of 5.6. Under the condition of a fixed aperture of 5.6, both the amount of light entering and the depth of field are taken into account, ensuring the reliable conversion of the projected light beam into an electrical signal.

[0038] In some embodiments of the present invention, the field of view of the compact wide-angle camera lens is not less than 100°. The image plane diameter of the image sensor 100 is not less than 43.2 mm. This parameter defines the effective light-gathering range and imaging boundary of the lens, ensuring that the large field of view light rays deflected by the lens group are completely received by the image sensor 100, and preventing the loss of edge light signals.

[0039] In one specific embodiment of this application, combined with Figure 2 The schematic diagram of the optical structure shown indicates that the compact wide-angle camera lens has a system focal length f of 18.1 mm, an aperture value FNO of 5.6, an image plane diameter of 43.2 mm, and a diagonal field of view of 100°. The lens surfaces along the optical axis from the object side to the image side are defined as S1 to S17, and the surface shape, radius of curvature, thickness interval, and corresponding lens material parameters of each optical surface are configured as shown in Table 1.

[0040] Table 1

[0041] Furthermore, in this embodiment, the fifth lens 50 is an aspherical plastic lens, and both its object-side surface S9 and image-side surface S10 are aspherical. The aspherical surface shape of the fifth lens 50 satisfies the following conic quadratic equation:

[0042] Where z is the sag of the aspherical surface along the optical axis at a height of y, c is the curvature of the vertex of the aspherical surface, y is the radial coordinate, and k is the conic conic coefficient. to These are the higher-order aspheric coefficients from the 4th to the 16th order.

[0043] Specifically, the object-side or image-side surface of the fifth lens 50 is shaped according to the curved surface profile defined by the above equation. During the transmission of the light beam through the fifth lens 50, compared to a sphere with a fixed curvature, the aspherical region defined by polynomials from the 4th to the 16th orders can provide differentiated deflection compensation for light rays incident at different radial coordinates y, specifically correcting the higher-order spherical aberration and astigmatism accumulated when light beams penetrate the lens at the edge of a large field of view, thus improving the lens's control accuracy for distortion at the edge of a large field of view. The specific values ​​of the corresponding conic coefficient K and the higher-order aspherical coefficients are shown in Table 2.

[0044] Table 2

[0045] Reference Figure 2 The optical structure and ray tracing path shown indicate that a large-angle incident beam from the object side first undergoes significant correction and smooth deflection via the first lens 10 and the second lens 20, then passes through the aperture ST positioned between surfaces S4 and S5. The light passing through the aperture ST undergoes preliminary chromatic aberration correction via the third lens 30 and the fourth lens 40, and then enters the meniscus-shaped fifth lens 50. The fifth lens 50 utilizes the aspherical surface features defined in Table 2 to locally deflect and compensate for light rays at the edge of the large field of view, further reducing system distortion. Subsequently, the beam enters the bonded lens group (with an internal bonding surface of S12) composed of the sixth lens 60 and the seventh lens 70, and the eighth lens 80, completing the final correction of chromatic aberration and aberrations, and is projected onto the image plane of the photosensitive chip 100 through the protective glass 90.

[0046] Reference Figure 3 The optical modulation transfer function (MTF) curve shown represents the contrast transfer characteristics of the lens at different spatial frequencies. Figure 3Based on the test data, it can be seen that the optical system of this embodiment has an imaging resolution greater than 0.6 under the condition of a spatial frequency of 30 lp / mm and a field of view of 0.5F or less; and an imaging resolution greater than 0.5 under the condition of a field of view of 0.8F or less. This data shows that the system has excellent center and edge imaging resolution, while the lens sensitivity is low. In mass production, the finished product resolution can be maintained above 0.4 within a field of view of 30 lp / mm and 0.8F.

[0047] Reference Figure 4 The field curvature and distortion diagram shown intuitively reflects the degree to which the lens's imaging plane deviates from the ideal plane and the offset rate of the image point position. Combined with the data in the diagram, it can be seen that at the ultra-wide-angle end with a diagonal field of view reaching 100°, the absolute value of the lens's optical distortion is effectively limited to within 2.6%, while the field curvature is controlled within a low offset range.

[0048] according to Figures 2 to 4 The comprehensive test results show that the optical power arrangement and glass-plastic hybrid structure of this embodiment, while limiting the total optical length to no more than 35mm, reduce system distortion by utilizing aspherical features, and, in conjunction with the bonded lens group and the eighth lens, complete the correction of chromatic aberration and aberration. The camera lens of this invention overcomes the shortcomings of the prior art in balancing a large field of view and a small volume, achieving the effect of expanding the field of view, reducing the volume, and ensuring image quality.

[0049] This application also provides an imaging device, including a body and a compact wide-angle camera lens as described in the above embodiments.

[0050] For example, a compact wide-angle camera lens is coaxially mounted to the front end of the camera body via a bayonet, flange, or threaded assembly. The camera body contains an image processing mainboard, and the image sensor 100 at the rear end of the compact wide-angle camera lens is connected to the image processing mainboard via a flexible printed circuit (FPC). A large-angle incident light beam from the external environment passes through the compact wide-angle camera lens, undergoes chromatic aberration and distortion correction via the specific optical power arrangement and aspherical feature combination described above, and is then projected onto the image plane of the image sensor 100. The light signal is converted into a digital electrical signal and transmitted to the image processing mainboard for processing and storage.

[0051] By configuring the compact wide-angle camera lens of the above embodiment, the imaging device effectively expands the field of view of the imaging device while limiting the overall size of the device, and reduces the image distortion rate in the edge field of view area, thereby improving the image quality.

[0052] Although preferred embodiments of the present application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the embodiments of the present application.

[0053] Finally, it should be noted that in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or terminal device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or terminal device. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or terminal device that includes said element.

[0054] The above provides a detailed description of a compact wide-angle camera lens and imaging device provided in this application. Specific examples have been used to illustrate the principles and implementation methods of this application. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A compact wide-angle camera lens, characterized in that, From the object side to the image side, the following are included in sequence: The first lens has negative optical power and the image side of the first lens is concave. A second lens, the second lens having positive optical power; Aperture; A third lens, wherein the third lens has positive optical power; A fourth lens, wherein the fourth lens has positive optical power; The fifth lens has a negative optical power; A bonded lens assembly, wherein the bonded lens assembly is formed by bonding together a sixth lens and a seventh lens having optical power; The eighth lens has positive optical power; The fifth lens is an aspherical plastic lens; the first lens, the second lens, the third lens, the fourth lens, the sixth lens, the seventh lens, and the eighth lens are all glass lenses.

2. The compact wide-angle camera lens according to claim 1, characterized in that, The first lens, the second lens, and the third lens are all convex-concave lenses; the fourth lens and the eighth lens are both biconvex lenses; and the fifth lens is a concave-convex lens.

3. The compact wide-angle camera lens according to claim 1 or 2, characterized in that, The object-side surface and image-side surface of the first lens, the second lens, the third lens, the fourth lens, the sixth lens, the seventh lens, and the eighth lens are all spherical.

4. The compact wide-angle camera lens according to claim 1, characterized in that, The focal length of the first lens is f1, the focal length of the second lens is f2, and the focal length of the third lens is f3, wherein |f1| < 23 mm; |f2| < 20 mm; and |f3| > 23 mm.

5. The compact wide-angle camera lens according to claim 4, characterized in that, The fourth lens has a focal length of f4, the fifth lens has a focal length of f5, the bonded lens group has a focal length of f6 / 7, and the eighth lens has a focal length of f8, wherein |f4| < 20mm; |f5| < 20mm; |f6 / 7| > 90mm; and |f8| > 40mm.

6. The compact wide-angle camera lens according to claim 1, characterized in that, The total optical length of the compact wide-angle camera lens is TTL, and the optical back focal length of the compact wide-angle camera lens is BFL, wherein TTL≤35mm; BFL≥12mm.

7. The compact wide-angle camera lens according to claim 1, characterized in that, The compact wide-angle camera lens is further provided with a protective glass and a photosensitive chip in sequence from the object side to the image side after the eighth lens; the aperture of the compact wide-angle camera lens corresponds to FNO 5.

6.

8. The compact wide-angle camera lens according to claim 7, characterized in that, The field of view of the compact wide-angle camera lens is not less than 100°; the image plane diameter of the photosensitive chip is not less than 43.2mm.

9. The compact wide-angle camera lens according to claim 1, characterized in that, The aspherical surface shape of the fifth lens satisfies the following conic quadratic equation: Where z is the sag of the aspherical surface along the optical axis at a height of y, c is the curvature of the vertex of the aspherical surface, y is the radial coordinate, and k is the conic conic coefficient. to These are the higher-order aspheric coefficients from the 4th to the 16th order.

10. An imaging device, characterized in that, Including the compact wide-angle camera lens as described in any one of claims 1 to 9.

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