Imaging lens

Abstract

The invention discloses an imaging lens. The imaging lens comprises a first lens group, a prism and a second lens group, wherein the first lens group has positive focal power and comprises a first lens with positive focal power, a second lens with positive focal power and a third lens with negative focal power which are sequentially arranged from the object side to the image side; the second lens group has positive focal power and comprises a fourth lens with negative focal power, a fifth lens with positive focal power, a sixth lens with positive focal power, a seventh lens with positive focal power and an eighth lens with negative focal power which are sequentially arranged from the object side to the image side; the prism is arranged between the first lens group and the second lens group; when the object distance changes, the imaging lens is focused by adjusting the position of the first lens group relative to the prism; the number of the lenses with the focal power of the imaging lens is eight.

Description

Technical Field

[0001] The present application relates to the field of optical devices, and in particular to an imaging lens. Background Art

[0002] Surveillance lenses are a key component in machine vision systems. Due to their high precision and high reliability, surveillance lenses are widely used in industrial automation and other fields. With the upgrading of the manufacturing industry and the development of intelligent manufacturing, the market demand for surveillance lenses has shown a steady growth trend, and higher requirements have been placed on surveillance lenses. For example, surveillance lenses need to have a wide range of object distances, high illumination, and high resolution.

[0003] However, surveillance lenses usually have some problems. For example, the surveillance lens has low resolution, low picture clarity, and poor imaging quality; or the surveillance lens has a narrow object distance and cannot meet the usage requirements of multiple scenarios; or the surveillance lens has low illumination and low picture color saturation; or the surveillance lens has large distortion and large picture deformation. Summary of the invention

[0004] On one hand, the present application provides an imaging lens, which includes a first lens group, a prism, and a second lens group; wherein the first lens group has positive optical power and includes a first lens with positive optical power, a second lens with positive optical power, and a third lens with negative optical power arranged in sequence from the object side to the image side; the second lens group has positive optical power and includes a fourth lens with negative optical power, a fifth lens with positive optical power, a sixth lens with positive optical power, a seventh lens with positive optical power, and an eighth lens with negative optical power arranged in sequence from the object side to the image side; the prism is arranged between the first lens group and the second lens group; when the object distance changes, the imaging lens is focused by adjusting the position of the first lens group relative to the prism; the number of lenses with optical power in the imaging lens is eight.

[0005] According to an exemplary embodiment of the present application, 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 convex. The object side surface of the third lens is concave. The object side surface of the fourth lens is concave, and the image side surface is concave. The object side surface of the fifth lens is convex, and the image side surface is convex. The object side surface of the sixth lens is convex, and the image side surface is convex. The object side surface of the seventh lens is convex, and the image side surface is convex. The object side surface of the eighth lens is concave, and the image side surface is concave.

[0006] According to an exemplary embodiment of the present application, the effective focal length FG1 of the first lens group and the total effective focal length F of the imaging lens satisfy: 1.75≤FG1 / F≤2.5.

[0007] According to an exemplary embodiment of the present application, the effective focal length FG2 of the second lens group and the total effective focal length F of the imaging lens satisfy: 0.45≤FG2 / F≤0.85.

[0008] According to an exemplary embodiment of the present application, the effective focal length FG1 of the first lens group and the effective focal length FG2 of the second lens group satisfy: 2.85≤FG1 / FG2≤3.1.

[0009] According to an exemplary embodiment of the present application, the effective focal length F1 of the first lens and the effective focal length FG1 of the first lens group satisfy: 0.95≤F1 / FG1≤3.29.

[0010] According to an exemplary embodiment of the present application, the effective focal length F2 of the second lens and the effective focal length FG1 of the first lens group satisfy: 0.59≤F2 / FG1≤1.31.

[0011] According to an exemplary embodiment of the present application, the effective focal length F3 of the third lens and the effective focal length FG1 of the first lens group satisfy: -1.77≤F3 / FG1≤-0.95.

[0012] According to an exemplary embodiment of the present application, the second lens and the third lens are cemented to form a first cemented lens, and the effective focal length FB1 of the first cemented lens and the effective focal length FG1 of the first lens group satisfy: 0.86≤FB1 / FG1≤5.78.

[0013] According to an exemplary embodiment of the present application, the effective focal length F4 of the fourth lens and the effective focal length FG2 of the second lens group satisfy: -0.42≤F4 / FG2≤-0.1.

[0014] According to an exemplary embodiment of the present application, the effective focal length F5 of the fifth lens and the effective focal length FG2 of the second lens group satisfy: 0.6≤F5 / FG2≤0.8.

[0015] According to an exemplary embodiment of the present application, the fourth lens and the fifth lens are cemented to form a second cemented lens, and the effective focal length FB2 of the second cemented lens and the effective focal length FG2 of the second lens group satisfy: -1.62≤FB2 / FG2≤-1.2.

[0016] According to an exemplary embodiment of the present application, the effective focal length F6 of the sixth lens and the effective focal length FG2 of the second lens group satisfy: 0.75≤F6 / FG2≤0.96.

[0017] According to an exemplary embodiment of the present application, the effective focal length F7 of the seventh lens and the effective focal length FG2 of the second lens group satisfy: 0.66≤F7 / FG2≤0.95.

[0018] According to an exemplary embodiment of the present application, the effective focal length F8 of the eighth lens and the effective focal length FG2 of the second lens group satisfy: -0.51≤F8 / FG2≤-0.33.

[0019] According to an exemplary embodiment of the present application, the seventh lens and the eighth lens are cemented to form a third cemented lens, and the effective focal length FB3 of the third cemented lens and the effective focal length FG2 of the second lens group satisfy: -2.2≤FB3 / FG2≤-1.8.

[0020] According to an exemplary embodiment of the present application, the effective focal length FG1 of the first lens group and the total optical length TTL of the imaging lens satisfy: 0.1≤FG1 / TTL≤0.94.

[0021] According to an exemplary embodiment of the present application, an axial distance T34 from the image side surface of the third lens to the object side surface of the fourth lens and a total effective focal length F of the imaging lens satisfy: 1.09≤T34 / F≤1.55.

[0022] According to an exemplary embodiment of the present application, the fourth lens and the fifth lens are cemented to form a second cemented lens, and the Abbe number V(B2) of at least one lens in the second cemented lens satisfies: 55≤V(B2)≤70.

[0023] According to an exemplary embodiment of the present application, the imaging lens satisfies at least one of the following conditional expressions:

[0024] 1.78≤FG1 / F≤2.39; 0.54≤FG2 / F≤0.84; 2.94≤FG1 / FG2≤3.12; 1.17≤F1 / FG1≤3.06; 0.61≤F2 / FG1≤1.29;-1.76≤F3 / FG1≤-1.16;1.41≤FB1 / FG1≤5.23;-0.43≤F4 / FG2≤-0.29;0.62≤F5 / F G2≤0.79; -1.64≤FB2 / FG2≤-1.42; 0.73≤F6 / FG2≤0.89; 0.65≤F7 / FG2≤0.85; -0.52≤F8 / FG2 ≤-0.36; -2.19≤FB3 / FG2≤-1.89; 0.70≤FG1 / TTL≤0.96; 1.07≤T34 / F≤1.23; 61≤V(B2)≤68.7;

[0025] Wherein, FG1 is the effective focal length of the first lens group, F is the total effective focal length of the imaging lens, FG2 is the effective focal length of the second lens group, F1 is the effective focal length of the first lens, F2 is the effective focal length of the second lens, F3 is the effective focal length of the third lens, FB1 is the effective focal length of the first cemented lens formed by cementing the second lens and the third lens, F4 is the effective focal length of the fourth lens, F5 is the effective focal length of the fifth lens, FB2 is the effective focal length of the second cemented lens formed by cementing the fourth lens and the fifth lens, F6 is the effective focal length of the sixth lens, F7 is the effective focal length of the seventh lens, F8 is the effective focal length of the eighth lens, FB3 is the effective focal length of the third cemented lens formed by cementing the seventh lens and the eighth lens, TTL is the total optical length of the imaging lens, T34 is the axial distance from the image side surface of the third lens to the object side surface of the fourth lens, and V(B2) is the Abbe number of at least one lens in the second cemented lens formed by cementing the fourth lens and the fifth lens.

[0026] According to an exemplary embodiment of the present application, the imaging lens also includes a first lens group replacement group; by switching the first lens group and the first lens group replacement group, focusing is achieved within the object distance range of 300 mm to infinity, wherein the first lens group achieves focusing within the object distance range of 500 mm to infinity; the first lens group replacement group achieves focusing within the object distance range of 300 mm to 600 mm.

[0027] According to an exemplary embodiment of the present application, the imaging lens includes a first imaging plane and a second imaging plane; the prism divides the light emitted by the first lens group into a first light beam and a second light beam; the first light beam is projected onto the first imaging plane via the second lens group; the imaging lens also includes a parallel second imaging lens group, and the second light beam is projected onto the second imaging plane via the parallel second lens group.

[0028] According to an exemplary embodiment of the present application, the imaging lens includes a first imaging plane and a second imaging plane; a prism divides light emitted from a first lens group into a first light beam and a second light beam; the first light beam is projected onto the first imaging plane via the second lens group; and the second light beam is projected onto the second imaging plane. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Other features, objects and advantages of the present application will become more apparent by reading the detailed description of non-limiting embodiments made with reference to the following drawings. In the drawings:

[0030] Figure 1 A schematic diagram of the imaging principle of the imaging lens 100 according to the present application is shown;

[0031] Figure 2 A schematic diagram of the imaging principle of the imaging lens 200 according to the present application is shown;

[0032] Figure 3 A schematic structural diagram of an imaging lens according to Embodiment 1 of the present application is shown;

[0033] Figure 4 shows a distortion curve when the imaging lens according to Embodiment 1 of the present application is in the third state;

[0034] Figure 5 shows a relative illumination curve when the imaging lens according to Embodiment 1 of the present application is in the third state;

[0035] Figure 6 A schematic structural diagram of an imaging lens according to Embodiment 2 of the present application is shown;

[0036] Figure 7 shows a distortion curve when the imaging lens according to Embodiment 2 of the present application is in the third state;

[0037] Figure 8 shows a relative illumination curve when the imaging lens according to Embodiment 2 of the present application is in the third state;

[0038] Fig. 9 A schematic structural diagram of an imaging lens according to Embodiment 3 of the present application is shown;

[0039] Fig.10 shows a distortion curve when the imaging lens according to Embodiment 3 of the present application is in the third state;

[0040] Fig.11 shows a relative illumination curve when the imaging lens according to Embodiment 3 of the present application is in the third state;

[0041] Fig.12 A schematic structural diagram of an imaging lens according to Embodiment 4 of the present application is shown;

[0042] Fig.13 shows a distortion curve when the imaging lens according to Embodiment 4 of the present application is in the third state;

[0043] Fig.14 FIG. 4 shows a relative illumination curve when the imaging lens according to Embodiment 4 of the present application is in the third state. DETAILED DESCRIPTION

[0044] In order to better understand the present application, various aspects of the present application are described in detail with reference to the accompanying drawings. It should be understood that these detailed descriptions are only descriptions of exemplary embodiments of the present application, and do not limit the scope of the present application in any way.

[0045] In the drawings, the thickness, size and shape of the lenses have been slightly exaggerated for ease of illustration. Specifically, the shapes of the spherical or aspherical surfaces shown in the drawings are shown by way of example. That is, the shapes of the spherical or aspherical surfaces are not limited to the shapes of the spherical or aspherical surfaces shown in the drawings. The drawings are for illustration only and are not drawn strictly to scale.

[0046] In this article, the paraxial region refers to the region near the optical axis. If the lens surface is convex and the position of the convex surface is not defined, it means that the lens surface is convex at least in the paraxial region; if the lens surface is concave and the position of the concave surface is not defined, it means that the lens surface is concave at least in the paraxial region. The surface of each lens closest to the object is called the object side of the lens, and the surface of each lens closest to the imaging plane is called the image side of the lens.

[0047] It should also be understood that the terms "include", "comprising", "having", "including" and / or "comprising", when used in this specification, indicate the presence of the stated features, elements and / or components, but do not exclude the presence or addition of one or more other features, elements, components and / or combinations thereof. It should be noted that in this specification, the expressions first, second, third, etc. are only used to distinguish one feature from another, and do not represent any limitation on the features. It should be noted that the longitudinal direction stated herein is the direction perpendicular to the optical axis.

[0048] Unless otherwise defined, all terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which this application belongs. Terms should be interpreted as having the same meaning as they have in the context of the relevant technology, and will not be interpreted in an idealized or overly formal sense unless explicitly defined in this article.

[0049] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0050] The imaging lens according to the exemplary embodiment of the present application may include a first lens group, a prism, and a second lens group, wherein the prism is disposed between the first lens group and the second lens group. The positions of the prism and the second lens group relative to the imaging surface on the image side on the optical axis are fixed. When the object distance changes, the imaging lens is focused by adjusting the position of the first lens group relative to the prism.

[0051] For example, when the distance between the object and the imaging lens changes from far to near, by adjusting the position of the first lens group relative to the prism, the imaging lens can be switched between different states, the focusing function of the imaging lens is realized, and the imaging lens can achieve clear focus within the range of 300 mm to infinity. For example, when the distance between the object and the imaging lens is a first preset value, the imaging lens is in a first state (e.g., a far object distance state); when the distance between the object and the imaging lens is a second preset value, the imaging lens is in a second state (e.g., an intermediate object distance state); when the distance between the object and the imaging lens is a third preset value, the imaging lens is in a third state (e.g., a close object distance state).

[0052] In an exemplary embodiment, the first lens group has positive power and includes a first lens having positive power, a second lens having positive power, and a third lens having negative power, arranged in order from the object side to the image side.

[0053] It should be understood that the number of lenses included in the first lens group being three is merely exemplary, and the present application does not impose any specific limitation on the number of lenses included in the first lens group.

[0054] In an exemplary embodiment, the second lens and the third lens are cemented to form a first cemented lens. By providing the first cemented lens, various aberrations of the imaging lens, especially chromatic aberration, astigmatism and field curvature, can be corrected, the resolution capability of the imaging lens can be improved, and the tolerance sensitivity of the imaging lens can be reduced, thereby achieving low distortion of the imaging lens.

[0055] In an exemplary embodiment, the second lens group has positive power and includes a fourth lens having negative power, a fifth lens having positive power, a sixth lens having positive power, a seventh lens having positive power, and an eighth lens having negative power, which are arranged in order from the object side to the image side. By setting the second lens group to have positive power, high resolution performance of the imaging lens can be achieved, distortion of the imaging lens can be reduced, and the field of view of the imaging lens can be increased.

[0056] It should be understood that the number of lenses included in the second lens group being five is merely exemplary, and the present application does not impose any specific limitation on the number of lenses included in the second lens group.

[0057] In an exemplary embodiment, the fourth lens and the fifth lens are cemented to form a second cemented lens. The seventh lens and the eighth lens are cemented to form a third cemented lens. By providing the second cemented lens and the third cemented lens, various aberrations of the imaging lens, especially chromatic aberration, astigmatism and field curvature, can be corrected, and the resolution capability of the imaging lens can be improved. At the same time, it is also beneficial to reduce the tolerance sensitivity of the imaging lens and achieve low distortion of the imaging lens.

[0058] In an exemplary embodiment, the imaging lens may further include a stop. The stop may be located between the prism and the second lens group.

[0059] In an exemplary embodiment, if Figure 1 As shown, the imaging lens 100 according to the present application may include a first imaging surface S301 and a second imaging surface S302. Light from the object surface OBJ passes through the first lens group S101 to the prism P. The prism P can separate the light emitted from the first lens group S101 into a first light beam LA and a second light beam LB. The first light beam LA is projected onto the first imaging surface S301 via the second lens group S201, and the second light beam LB is projected onto the second imaging surface S302.

[0060] In an exemplary embodiment, if Figure 1 As shown, as needed, the imaging lens 100 may further include a parallel second lens group S202. The light from the object plane OBJ passes through the first lens group S101 to the prism P. The prism P can split the light emitted from the first lens group S101 into a first light beam LA and a second light beam LB. The first light beam LA is projected onto the first imaging plane S301 via the second lens group S201, and the second light beam LB is projected onto the second imaging plane S302 via the parallel second lens group S202.

[0061] In an exemplary embodiment, if Figure 2 As shown, the imaging lens 200 according to the present application may further include a first lens group replacement group S102. When the object distance changes, by switching the first lens group S101 and the first lens group replacement group S102, the imaging lens 200 can achieve focusing within the object distance range of 300 mm to infinity, wherein the first lens group S101 focuses within the object distance range of 500 mm to infinity, and the first lens group replacement group S102 focuses within the object distance range of 300 mm to 600 mm.

[0062] In an exemplary embodiment, if Figure 2 As shown, the imaging lens 200 may be provided with or without the parallel second lens group S202 as required. Light from the object plane OBJ passes through the first lens group S101 or the first lens group replacement group S102 to the prism P. The prism P can separate the light emitted from the first lens group S101 or the first lens group replacement group S102 into a first light beam LA and a second light beam LB. The first light beam LA is projected onto the first imaging surface S301 via the second lens group S201. The second light beam LB is projected onto the second imaging surface S302 via the parallel second lens group S202 or directly.

[0063] It should be understood by those skilled in the art that although Figure 1 and Figure 2In the embodiment, the prism is used to divide the light emitted by the first lens group S101 into two light beams for explanation, but this does not limit the scope of the present application. In other embodiments of the present application, the prism can also divide the light emitted by the first lens group S101 into more light beams, and fixed groups or parallel fixed groups can be set on different optical paths behind the prism as needed.

[0064] The present application utilizes a prism to split the light emitted from the first lens group, thereby realizing multi-beam imaging of the imaging lens. In addition, the use of a prism can also increase the length of the light beam, facilitating the arrangement of components such as the second lens group and the aperture.

[0065] In an exemplary embodiment, the effective focal length FG1 of the first lens group and the total effective focal length F of the imaging lens may satisfy: 1.75≤FG1 / F≤2.5. In one example, 1.78≤FG1 / F≤2.39. By properly configuring the ratio of the effective focal length of the first lens group to the total effective focal length of the imaging lens, the focusing function of the imaging lens can be realized by moving the first lens group when the object distance changes, and the imaging lens can be clearly focused within the range of 300 mm to infinity, so that different light beams of the imaging lens are clearly focused at the same time.

[0066] In an exemplary embodiment, the effective focal length FG2 of the second lens group and the total effective focal length F of the imaging lens may satisfy: 0.45≤FG2 / F≤0.85. In one example, 0.54≤FG2 / F≤0.84. Reasonable configuration of the ratio of the effective focal length of the second lens group to the total effective focal length of the imaging lens is conducive to expanding the field of view of the imaging lens, and is also conducive to achieving high resolution and low distortion of the imaging lens. For example, the absolute value of the optical distortion DIS of the imaging lens satisfies |DIS|≤2.5%.

[0067] In an exemplary embodiment, the effective focal length FG1 of the first lens group and the effective focal length FG2 of the second lens group may satisfy: 2.85≤FG1 / FG2≤3.1. In one example, 2.94≤FG1 / FG2≤3.12. Reasonable configuration of the ratio of the effective focal length of the first lens group to the effective focal length of the second lens group is conducive to the clear focus of the imaging lens in the range of 300 mm to infinity.

[0068] In an exemplary embodiment, the effective focal length F1 of the first lens and the effective focal length FG1 of the first lens group may satisfy: 0.95≤F1 / FG1≤3.29. In one example, 1.17≤F1 / FG1≤3.06. Reasonable configuration of the ratio of the effective focal length of the first lens to the effective focal length of the first lens group can properly converge the light from the object side, so that the first lens bears the main focal power of the first lens group, which is conducive to correcting aberrations and achieving high resolution performance of the imaging lens.

[0069] In an exemplary embodiment, the effective focal length F2 of the second lens and the effective focal length FG1 of the first lens group may satisfy: 0.59≤F2 / FG1≤1.31. In one example, 0.61≤F2 / FG1≤1.29. Reasonable configuration of the ratio of the effective focal length of the second lens to the effective focal length of the first lens group can make the second lens have positive focal power, which is conducive to correcting chromatic aberration and improving the image quality of the imaging lens.

[0070] In an exemplary embodiment, the effective focal length F3 of the third lens and the effective focal length FG1 of the first lens group may satisfy: -1.77≤F3 / FG1≤-0.95. In one example, -1.76≤F3 / FG1≤-1.16. Reasonable configuration of the ratio of the effective focal length of the third lens to the effective focal length of the first lens group can make the third lens have negative optical power, which is beneficial to correct chromatic aberration and improve the image quality of the imaging lens.

[0071] In an exemplary embodiment, the effective focal length FB1 of the first cemented lens formed by the second lens and the third lens and the effective focal length FG1 of the first lens group may satisfy: 0.86≤FB1 / FG1≤5.78. In one example, 1.41≤FB1 / FG1≤5.23. Reasonable configuration of the ratio of the effective focal length of the first cemented lens to the effective focal length of the first lens group can correct the chromatic aberration of the imaging lens and improve the resolution of the imaging lens.

[0072] In an exemplary embodiment, the effective focal length F4 of the fourth lens and the effective focal length FG2 of the second lens group may satisfy: -0.42≤F4 / FG2≤-0.1. In one example, -0.43≤F4 / FG2≤-0.29. Reasonable configuration of the ratio of the effective focal length of the fourth lens to the effective focal length of the second lens group is conducive to correcting the field curvature and astigmatism of the imaging lens, improving the resolution performance of the imaging lens, and achieving low distortion of the imaging lens.

[0073] In an exemplary embodiment, the effective focal length F5 of the fifth lens and the effective focal length FG2 of the second lens group may satisfy: 0.6≤F5 / FG2≤0.8. In one example, 0.62≤F5 / FG2≤0.79. Reasonable configuration of the ratio of the effective focal length F5 of the fifth lens to the effective focal length of the second lens group, and the use of the fifth lens in conjunction with the fourth lens having a negative optical power, is conducive to correcting the chromatic aberration of the imaging lens, improving the resolution performance of the imaging lens, and achieving low distortion of the imaging lens.

[0074] In an exemplary embodiment, the effective focal length FB2 of the second cemented lens formed by the fourth lens and the fifth lens and the effective focal length FG2 of the second lens group may satisfy: -1.62≤FB2 / FG2≤-1.2. In one example, -1.64≤FB2 / FG2≤-1.42. Reasonable configuration of the ratio of the effective focal length of the second cemented lens to the effective focal length of the second lens group is conducive to correcting the chromatic aberration of the imaging lens and improving the resolution performance of the imaging lens.

[0075] In an exemplary embodiment, the effective focal length F6 of the sixth lens and the effective focal length FG2 of the second lens group may satisfy: 0.75≤F6 / FG2≤0.96. In one example, 0.73≤F6 / FG2≤0.89. Reasonable configuration of the ratio of the effective focal length of the sixth lens to the effective focal length of the second lens group can effectively control the light trend, so that the light smoothly transitions to the rear system, avoids excessive increase in aberrations, and enables the imaging lens to have high image quality and high relative illumination.

[0076] In an exemplary embodiment, the effective focal length F7 of the seventh lens and the effective focal length FG2 of the second lens group may satisfy: 0.66≤F7 / FG2≤0.95. In one example, 0.65≤F7 / FG2≤0.85. Reasonable configuration of the ratio of the effective focal length F7 of the seventh lens to the effective focal length of the second lens group enables the seventh lens to bear a larger optical power in the second lens group and properly converge the light emitted by the sixth lens, which is conducive to correcting aberrations, especially astigmatism and field curvature, and improving the resolution performance of the imaging lens.

[0077] In an exemplary embodiment, the effective focal length F8 of the eighth lens and the effective focal length FG2 of the second lens group may satisfy: -0.51≤F8 / FG2≤-0.33. In one example, -0.52≤F8 / FG2≤-0.36. By properly configuring the ratio of the effective focal length of the eighth lens to the effective focal length of the second lens group, and using the eighth lens in conjunction with the seventh lens having positive power, the chromatic aberration of the imaging lens can be effectively corrected, and the resolution performance of the imaging lens can be improved.

[0078] In an exemplary embodiment, the effective focal length FB3 of the third cemented lens formed by the seventh lens and the eighth lens and the effective focal length FG2 of the second lens group may satisfy: -2.2≤FB3 / FG2≤-1.8. In one example, -2.19≤FB3 / FG2≤-1.89. Reasonable configuration of the ratio of the effective focal length of the third cemented lens to the effective focal length of the second lens group is conducive to reducing the chromatic aberration of the imaging lens and improving the relative illumination of the imaging lens. For example, the relative illumination RI satisfies RI≥70%.

[0079] In an exemplary embodiment, the effective focal length FG1 of the first lens group and the total optical length TTL of the imaging lens may satisfy: 0.1≤FG1 / TTL≤0.94. In one example, 0.70≤FG1 / TTL≤0.96. Reasonable configuration of the ratio of the effective focal length of the first lens group to the total optical length of the imaging lens is conducive to controlling the total optical length of the first lens group and realizing miniaturization of the imaging lens.

[0080] In an exemplary embodiment, the on-axis distance T34 from the image side surface of the third lens to the object side surface of the fourth lens and the total effective focal length F of the imaging lens may satisfy: 1.09≤T34 / F≤1.55. In one example, 1.07≤T34 / F≤1.23. Reasonable configuration of the ratio of the on-axis distance from the image side surface of the third lens to the object side surface of the fourth lens to the total effective focal length of the imaging lens is conducive to reserving sufficient installation space for the prism and realizing the miniaturization of the imaging lens.

[0081] In an exemplary embodiment, the Abbe number V(B2) of at least one lens in the second cemented lens formed by the fourth lens and the fifth lens may satisfy: 55≤V(B2)≤70. In one example, 61≤V(B2)≤68.7. Reasonable configuration of the Abbe number of at least one lens in the second cemented lens is conducive to correcting various aberrations of the imaging lens, especially spherical aberration and chromatic aberration, and achieving high resolution of the imaging lens.

[0082] In an exemplary embodiment, the imaging lens may further include a filter for correcting color deviation.

[0083] In an exemplary embodiment, any one of the first lens to the eighth lens is a glass lens. The glass lens can effectively suppress the deviation of the back focal length of the imaging lens due to temperature changes, and improve the stability of the imaging lens; at the same time, the glass lens can effectively avoid the problem of imaging blur caused by high temperature or low temperature environment, ensure that the imaging lens has a high light transmittance, and is conducive to better correction of system chromatic aberration, and improve the resolution of the imaging lens; at the same time, a lower manufacturing cost is achieved.

[0084] However, those skilled in the art should understand that, without departing from the technical solution claimed in the present application, the number of lenses constituting the imaging lens can be changed to obtain the various results and advantages described in this specification.

[0085] Specific embodiments of the imaging lens applicable to the above-mentioned embodiments are further described below with reference to the accompanying drawings.

[0086] Example 1

[0087] The following reference Figure 3 An imaging lens according to Embodiment 1 of the present application is described. Figure 3Schematic diagram of the structure of an imaging lens according to Embodiment 1 of the present application.

[0088] like Figure 3 As shown, the imaging lens includes a first lens group, a prism P and a second lens group. The first lens group includes a first lens L1, a second lens L2 and a third lens L3. The second lens group includes a fourth lens L4, a fifth lens L5, a sixth lens L6, a seventh lens L7 and an eighth lens L8. The aperture STO is arranged between the prism P and the second lens group. The second lens L2 and the third lens L3 are cemented to form a first cemented lens. The fourth lens L4 and the fifth lens L5 are cemented to form a second cemented lens. The seventh lens L7 and the eighth lens L8 are cemented to form a third cemented lens.

[0089] The first lens L1 has positive refractive power, an object-side surface S1 of which is convex, and an image-side surface S2 of which is concave.

[0090] The second lens L2 has positive refractive power, and its object-side surface S3 is convex, and its image-side surface S4 is convex.

[0091] The third lens L3 has negative refractive power, and its object-side surface is concave, and its image-side surface S5 is concave.

[0092] The object-side surface S6 and the image-side surface S7 of the prism P are planes.

[0093] The fourth lens L4 has negative refractive power, and its object-side surface S9 is concave, and its image-side surface S10 is concave.

[0094] The fifth lens L5 has positive refractive power, and its object-side surface is convex, and its image-side surface S11 is convex.

[0095] The sixth lens L6 has positive refractive power, and its object-side surface S12 is convex, and its image-side surface S13 is convex.

[0096] The seventh lens L7 has positive refractive power, and its object-side surface S14 is convex, and its image-side surface S15 is convex.

[0097] The eighth lens L8 has negative refractive power, and its object-side surface is concave, and its image-side surface S16 is concave.

[0098] A filter CG may also be provided between the eighth lens L8 and the imaging surface IMA. The filter CG has an object side surface S17 and an image side surface S18. Light from the object passes through the surfaces S1-S7, S9-S18 in sequence and is finally imaged on the imaging surface IMA. It should be noted that the surfaces S1-S7, S9-S18 are Figure 3 Not shown.

[0099] Table 1 shows the basic parameters of the imaging lens of Example 1, wherein the units of the radius of curvature and thickness / distance are all millimeters (mm).

[0100]

[0101]

[0102] Table 1

[0103] In this embodiment, the imaging lens has a first state, a second state and a third state. The distance between the object plane and the imaging lens (i.e., the object distance) is D1, and the distance between the first lens group and the prism is D2. D1 and D2 are variables, which may change as the state of the imaging lens changes.

[0104] Table 2 shows the values ​​of D1, D2 and the total effective focal length F of the imaging lens in different states of the imaging lens in Example 1. The units of D1, D2 and F are all millimeters (mm).

[0105] Separation distance First State Second State The third state D1 600.000 400.000 300.000 D2 5.280 6.822 8.511 F 18.904 20.031 21.430

[0106] Table 2

[0107] Figure 4 FIG. 4 shows a distortion curve when the imaging lens of Example 1 is in the third state. Figure 5 FIG. 2 shows a relative illumination curve when the imaging lens of Example 1 is in the third state. Figure 4 and Figure 5 It can be seen that good imaging quality can be achieved when the imaging lens is in the third state.

[0108] Example 2

[0109] The following reference Figure 6 An imaging lens according to Embodiment 2 of the present application is described. Figure 6 Schematic diagram of the structure of an imaging lens according to Embodiment 2 of the present application.

[0110] like Figure 6 As shown, the imaging lens includes a first lens group, a prism P and a second lens group. The first lens group includes a first lens L1, a second lens L2 and a third lens L3. The second lens group includes a fourth lens L4, a fifth lens L5, a sixth lens L6, a seventh lens L7 and an eighth lens L8. The aperture STO is arranged between the prism P and the second lens group. The second lens L2 and the third lens L3 are cemented to form a first cemented lens. The fourth lens L4 and the fifth lens L5 are cemented to form a second cemented lens. The seventh lens L7 and the eighth lens L8 are cemented to form a third cemented lens.

[0111] The first lens L1 has positive refractive power, an object-side surface S1 of which is convex, and an image-side surface S2 of which is concave.

[0112] The second lens L2 has positive refractive power, and its object-side surface S3 is convex, and its image-side surface S4 is convex.

[0113] The third lens L3 has negative refractive power, and its object-side surface is concave, and its image-side surface S5 is concave.

[0114] The object-side surface S6 and the image-side surface S7 of the prism P are planes.

[0115] The fourth lens L4 has negative refractive power, and its object-side surface S9 is concave, and its image-side surface S10 is concave.

[0116] The fifth lens L5 has positive refractive power, and its object-side surface is convex, and its image-side surface S11 is convex.

[0117] The sixth lens L6 has positive refractive power, and its object-side surface S12 is convex, and its image-side surface S13 is convex.

[0118] The seventh lens L7 has positive refractive power, and its object-side surface S14 is convex, and its image-side surface S15 is convex.

[0119] The eighth lens L8 has negative refractive power, and its object-side surface is concave, and its image-side surface S16 is concave.

[0120] A filter CG may also be provided between the eighth lens L8 and the imaging surface IMA. The filter CG has an object side surface S17 and an image side surface S18. Light from the object passes through the surfaces S1-S7, S9-S18 in sequence and is finally imaged on the imaging surface IMA. It should be noted that the surfaces S1-S7, S9-S18 are Figure 6 Not shown.

[0121] Table 3 shows the basic parameters of the imaging lens of Example 2, wherein the units of the radius of curvature and thickness / distance are all millimeters (mm).

[0122]

[0123] Table 3

[0124] In this embodiment, the imaging lens has a first state, a second state and a third state. The distance between the object plane and the imaging lens (i.e., the object distance) is D1, and the distance between the first lens group and the prism is D2. D1 and D2 are variables, which may change as the state of the imaging lens changes.

[0125] Table 4 shows the values ​​of D1, D2 and the total effective focal length F of the imaging lens under different states of the imaging lens in Example 2. The units of D1, D2 and F are all millimeters (mm).

[0126]

[0127]

[0128] Table 4

[0129] Figure 7 FIG. 4 shows a distortion curve of the imaging lens of Example 2 when it is in the third state. Figure 8 FIG. 2 shows a relative illumination curve of the imaging lens of Embodiment 2 when it is in the third state. Figure 7 and Figure 8 It can be seen that good imaging quality can be achieved when the imaging lens is in the third state.

[0130] Example 3

[0131] The following reference Fig. 9 An imaging lens according to Embodiment 3 of the present application is described. Fig. 9 Schematic diagram of the structure of an imaging lens according to Embodiment 3 of the present application.

[0132] like Fig. 9 As shown, the imaging lens includes a first lens group, a prism P and a second lens group. The first lens group includes a first lens L1, a second lens L2 and a third lens L3. The second lens group includes a fourth lens L4, a fifth lens L5, a sixth lens L6, a seventh lens L7 and an eighth lens L8. The aperture STO is arranged between the prism P and the second lens group. The second lens L2 and the third lens L3 are cemented to form a first cemented lens. The fourth lens L4 and the fifth lens L5 are cemented to form a second cemented lens. The seventh lens L7 and the eighth lens L8 are cemented to form a third cemented lens.

[0133] The first lens L1 has positive refractive power, an object-side surface S1 of which is convex, and an image-side surface S2 of which is flat.

[0134] The second lens L2 has positive refractive power, and its object-side surface S3 is convex, and its image-side surface S4 is convex.

[0135] The third lens L3 has negative refractive power, its object-side surface is concave, and its image-side surface S5 is flat.

[0136] The object-side surface S6 and the image-side surface S7 of the prism P are planes.

[0137] The fourth lens L4 has negative refractive power, and its object-side surface S9 is concave, and its image-side surface S10 is concave.

[0138] The fifth lens L5 has positive refractive power, and its object-side surface is convex, and its image-side surface S11 is convex.

[0139] The sixth lens L6 has positive refractive power, and its object-side surface S12 is convex, and its image-side surface S13 is convex.

[0140] The seventh lens L7 has positive refractive power, and its object-side surface S14 is convex, and its image-side surface S15 is convex.

[0141] The eighth lens L8 has negative refractive power, and its object-side surface is concave, and its image-side surface S16 is concave.

[0142] A filter CG may also be provided between the eighth lens L8 and the imaging surface IMA. The filter CG has an object side surface S17 and an image side surface S18. Light from the object passes through the surfaces S1-S7, S9-S18 in sequence and is finally imaged on the imaging surface IMA. It should be noted that the surfaces S1-S7, S9-S18 are Fig. 9 Not shown.

[0143] Table 5 shows the basic parameter table of the imaging lens of Example 3, wherein the units of the curvature radius and thickness / distance are all millimeters (mm).

[0144]

[0145]

[0146] Table 5

[0147] In this embodiment, the imaging lens has a first state, a second state and a third state. The distance between the object plane and the imaging lens (i.e., the object distance) is D1, and the distance between the first lens group and the prism is D2. D1 and D2 are variables, which may change as the state of the imaging lens changes.

[0148] Table 6 shows the values ​​of D1, D2 and the total effective focal length F of the imaging lens under different states of the imaging lens in Example 3. The units of D1, D2 and F are all millimeters (mm).

[0149] Separation distance First State Second State The third state D1 600.000 400.000 300.000 D2 5.266 6.816 8.478 F 18.896 20.012 21.365

[0150] Table 6

[0151] Fig.10 FIG. 4 shows a distortion curve when the imaging lens of Example 3 is in the third state. Fig.11 FIG. 4 shows a relative illumination curve when the imaging lens of Example 3 is in the third state. Fig.10 and Fig.11 It can be seen that good imaging quality can be achieved when the imaging lens is in the third state.

[0152] Example 4

[0153] The following reference Fig.12 An imaging lens according to Embodiment 4 of the present application is described. Fig.12 Schematic diagram of the structure of an imaging lens according to Embodiment 4 of the present application.

[0154] like Fig.12 As shown, the imaging lens includes a first lens group, a prism P and a second lens group. The first lens group includes a first lens L1, a second lens L2 and a third lens L3. The second lens group includes a fourth lens L4, a fifth lens L5, a sixth lens L6, a seventh lens L7 and an eighth lens L8. The aperture STO is arranged between the prism and the fourth lens L4. The second lens L2 and the third lens L3 are cemented to form a cemented lens. The fourth lens L4 and the fifth lens L5 are cemented to form a cemented lens. The seventh lens L7 and the eighth lens L8 are cemented to form a cemented lens.

[0155] The first lens L1 has positive refractive power, an object-side surface S1 of which is convex, and an image-side surface S2 of which is flat.

[0156] The second lens L2 has positive refractive power, and its object-side surface S3 is convex, and its image-side surface S4 is convex.

[0157] The third lens L3 has negative refractive power, its object-side surface is concave, and its image-side surface S5 is flat.

[0158] The object-side surface S6 and the image-side surface S7 of the prism P are planes.

[0159] The fourth lens L4 has negative refractive power, and its object-side surface S9 is concave, and its image-side surface S10 is concave.

[0160] The fifth lens L5 has positive refractive power, and its object-side surface is convex, and its image-side surface S11 is convex.

[0161] The sixth lens L6 has positive refractive power, and its object-side surface S12 is convex, and its image-side surface S13 is convex.

[0162] The seventh lens L7 has positive refractive power, and its object-side surface S14 is convex, and its image-side surface S15 is convex.

[0163] The eighth lens L8 has negative refractive power, and its object-side surface is concave, and its image-side surface S16 is concave.

[0164] A filter CG may also be provided between the eighth lens L8 and the imaging surface IMA. The filter CG has an object side surface S17 and an image side surface S18. Light from the object passes through the surfaces S1-S7, S9-S18 in sequence and is finally imaged on the imaging surface IMA. It should be noted that the surfaces S1-S7, S9-S18 are Fig.12 Not shown.

[0165] Table 7 shows the basic parameter table of the imaging lens of Example 4, wherein the units of the radius of curvature and thickness / distance are all millimeters (mm).

[0166]

[0167] Table 7

[0168] In this embodiment, the imaging lens has a first state, a second state and a third state. The distance between the object plane and the imaging lens (i.e., the object distance) is D1, and the distance between the first lens group and the prism is D2. D1 and D2 are variables, which may change as the state of the imaging lens changes.

[0169] Table 8 shows the values ​​of D1, D2 and the total effective focal length F of the imaging lens under different states of the imaging lens in Example 4. The units of D1, D2 and F are all millimeters (mm).

[0170] Separation distance First State Second State The third state D1 Infinity 3000.000 500.000 D2 3.962 4.493 7.361 F 17.155 17.457 19.299

[0171] Table 8

[0172] Fig.13 FIG. 4 shows a distortion curve when the imaging lens of Example 4 is in the third state. Fig.14 FIG. 4 shows a relative illumination curve when the imaging lens of Example 4 is in the third state. Fig.13 and Fig.14 It can be seen that good imaging quality can be achieved when the imaging lens is in the third state.

[0173] In summary, the conditional expressions in embodiments 1 to 4 satisfy the relationship shown in Table 9. Wherein, F in FG1 / F, FG2 / F, and T34 / F in Table 9 may be, for example, the total effective focal length of the imaging lens when it is in the third state.

[0174] Conditional / Example 1 2 3 4 FG1 / F 1.857 2.319 1.857 2.310 FG2 / F 0.610 0.762 0.616 0.767 FG1 / FG2 3.045 3.043 3.015 3.013 F1 / FG1 1.396 2.976 1.307 2.992 F2 / FG1 0.989 0.687 1.222 0.789 F3 / FG1 -1.339 -1.236 -1.692 -1.631 FB1 / FG1 3.532 1.486 4.213 1.485 F4 / FG2 -0.361 -0.361 -0.365 -0.365 F5 / FG2 0.689 0.689 0.716 0.716 FB2 / FG2 -1.520 -1.520 -1.488 -1.488 F6 / FG2 0.803 0.803 0.824 0.824 F7 / FG2 0.748 0.748 0.718 0.718 F8 / FG2 -0.451 -0.451 -0.428 -0.428 FB3 / FG2 -1.997 -1.997 -2.116 -2.116 FG1 / TTL 0.776 0.885 0.766 0.867 T34 / F 1.146 1.165 1.142 1.160 V(B2) 61.250 61.250 68.630 68.630

[0175] Table 9

[0176] The present application also provides an imaging device, whose electronic photosensitive element may be a charge coupled device (CCD) or a complementary metal oxide semiconductor (CMOS), and the imaging device is equipped with the imaging lens described above.

[0177] The above description is only a preferred embodiment of the present application and an explanation of the technical principles used. Those skilled in the art should understand that the scope of the invention involved in the present application is not limited to the technical solution formed by a specific combination of the above technical features, but should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the inventive concept. For example, the above features are replaced with the technical features with similar functions disclosed in this application (but not limited to) by each other.

Claims

1. An imaging lens, characterized in that: It includes a first lens group, a prism and a second lens group; wherein, The first lens group has positive refractive power and includes a first lens with positive refractive power, a second lens with positive refractive power, and a third lens with negative refractive power, which are arranged in sequence from the object side to the image side; The second lens group has positive power and includes, arranged in order from the object side to the image side, a fourth lens having negative power, a fifth lens having positive power, a sixth lens having positive power, a seventh lens having positive power, and an eighth lens having negative power; The prism is disposed between the first lens group and the second lens group; When the object distance changes, the imaging lens is focused by adjusting the position of the first lens group relative to the prism; The number of lenses having optical power of the imaging lens is eight.

2. The imaging lens according to claim 1, characterized in that: The object side surface of the first lens is a convex surface; The object side surface of the second lens is convex, and the image side surface is convex; The object side surface of the third lens is a concave surface; The object side surface of the fourth lens is concave, and the image side surface is concave; The object side surface of the fifth lens is convex, and the image side surface is convex; The object side surface of the sixth lens is convex, and the image side surface is convex; The object side surface of the seventh lens is convex, and the image side surface is convex; The object side surface of the eighth lens is concave, and the image side surface is concave.

3. The imaging lens according to claim 1 or 2, characterized in that: The effective focal length FG1 of the first lens group and the total effective focal length F of the imaging lens satisfy: 1.75≤FG1 / F≤2.

5.

4. The imaging lens according to claim 1 or 2, characterized in that: The effective focal length FG2 of the second lens group and the total effective focal length F of the imaging lens satisfy: 0.45≤FG2 / F≤0.

85.

5. The imaging lens according to claim 1 or 2, characterized in that: The effective focal length FG1 of the first lens group and the effective focal length FG2 of the second lens group satisfy: 2.85≤FG1 / FG2≤3.

1.

6. The imaging lens according to claim 1 or 2, characterized in that: The effective focal length F1 of the first lens and the effective focal length FG1 of the first lens group satisfy: 0.95≤F1 / FG1≤3.

29.

7. The imaging lens according to claim 1 or 2, characterized in that: The effective focal length F2 of the second lens and the effective focal length FG1 of the first lens group satisfy: 0.59≤F2 / FG1≤1.

31.

8. The imaging lens according to claim 1 or 2, characterized in that: The effective focal length F3 of the third lens and the effective focal length FG1 of the first lens group satisfy: -1.77≤F3 / FG1≤-0.

95.

9. The imaging lens according to claim 1 or 2, characterized in that: The second lens and the third lens are cemented to form a first cemented lens, and an effective focal length FB1 of the first cemented lens and an effective focal length FG1 of the first lens group satisfy: 0.86≤FB1 / FG1≤5.

78.

10. The imaging lens according to claim 1 or 2, characterized in that: The effective focal length F4 of the fourth lens and the effective focal length FG2 of the second lens group satisfy: -0.42≤F4 / FG2≤-0.1.

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