Imaging lens

Abstract

Provided is an imaging lens comprising, in order from an object side to an image side along an optical axis, a first lens, a prism, a second lens, a third lens, a fourth lens, a fifth lens, and a sixth lens. The first lens is disposed on an incident light side of the prism, the second lens to the sixth lens are disposed on an emergent light side of the prism, and the optical axis is bent on a reflecting surface of the prism. The imaging lens has a total of six lenses with refractive powers, the first lens to the sixth lens are all aspherical lenses, and the refractive powers are positive, positive, negative, positive, positive, and negative, respectively. A ratio of a focal length of the first lens to a distance between the prism and the second lens on the optical axis is greater than or equal to 4 and less than or equal to 60.

Description

Technical Field

[0001] This invention relates to optical devices, and more particularly to image-capturing lenses. Background Technology

[0002] With the widespread adoption of smartphones, using smartphones for photography has become the mainstream in the camera market. However, due to the limited thickness of smartphones, the image-taking lens cannot protrude significantly from the phone body, resulting in fewer telephoto lenses being used on smartphones. Summary of the Invention

[0003] This invention provides a telephoto lens that is small in size and has excellent optical performance.

[0004] According to an embodiment of the present invention, an imaging lens is provided, comprising, in sequence along the optical axis from the object side to the image side, a first lens, a prism, a second lens, a third lens, a fourth lens, a fifth lens, and a sixth lens. The first lens is disposed on the light-incident side of the prism, and the second to sixth lenses are disposed on the light-outcrystal side of the prism, with the optical axis reversing on the reflecting surface of the prism. The imaging lens comprises six lenses with refractive power, and the first to sixth lenses are all aspherical lenses with refractive powers of positive, positive, negative, positive, positive, and negative, respectively. The ratio of the focal length of the first lens to the distance between the prism and the second lens on the optical axis is greater than or equal to 4 and less than or equal to 60.

[0005] Based on the above, the imaging lens provided in this embodiment of the invention has a first lens disposed on the light-incident side of the prism to converge the light, and a second to a sixth lens disposed on the light-outcrystal side of the prism. The imaging lens can be used in smartphones and has a large effective focal length.

[0006] To make the above features and advantages of the present invention more apparent and understandable, specific embodiments are described below in conjunction with the accompanying drawings. Attached Figure Description

[0007] Figure 1A A schematic diagram of the imaging lens in a first focusing state according to a first embodiment of the present invention is shown. Figure 1B and Figure 1C for Figure 1A A schematic diagram of the field curvature of the imaging lens. Figure 1D for Figure 1A A schematic diagram of image sensor distortion;

[0008] Figure 2A A schematic diagram of the imaging lens in a second focusing state according to a first embodiment of the present invention is shown. Figure 2B and Figure 2C for Figure 2A A schematic diagram of the field curvature of the imaging lens. Figure 2D for Figure 2AA schematic diagram of image sensor distortion;

[0009] Figure 3A A schematic diagram of the imaging lens in a first focusing state according to a second embodiment of the present invention is shown. Figure 3B and Figure 3C for Figure 3A A schematic diagram of the field curvature of the imaging lens. Figure 3D for Figure 3A A schematic diagram of image sensor distortion;

[0010] Figure 4A A schematic diagram of the imaging lens in a second focusing state according to a second embodiment of the present invention is shown. Figure 4B and Figure 4C for Figure 4A A schematic diagram of the field curvature of the imaging lens. Figure 4D for Figure 4A A schematic diagram of the distortion of the imaging lens.

[0011] Explanation of icon numbers:

[0012] 0: Aperture

[0013] 1, 2, 3, 4, 5, 6: Lenses

[0014] 7: Prism

[0015] 8: Filters

[0016] 10, 20: Image capture lens

[0017] 15, 25, 35, 45, 55, 65, 85: Side view of the object

[0018] 16, 26, 36, 46, 56, 66, 86: side view

[0019] 75: Light-receiving surface

[0020] 76: Exposed surface

[0021] 77: Reflective surface

[0022] 99: Imaging plane

[0023] A1, A2, A3: Direction

[0024] I: optical axis Detailed Implementation

[0025] Reference Figure 1AThis diagram illustrates an imaging lens in a first focusing state according to a first embodiment of the present invention. The imaging lens 10, from the object side to the image side along the optical axis I, sequentially includes a lens 1, a prism 7, a lens 2, a lens 3, a lens 4, a lens 5, a lens 6, and a filter 8. Each of the lenses 1, 2, 3, 4, 5, 6, and the filter 8 has an object-side surface 15, 25, 35, 45, 55, 65, 85 through which imaging light passes, and an image-side surface 16, 26, 36, 46, 56, 66, 86 through which imaging light passes. The refractive powers of lenses 1, 2, 3, 4, 5, and 6 are positive, positive, negative, positive, positive, and negative, respectively, and all lenses 1 to 6 are aspherical lenses. The object side described above is in the positive direction A1 relative to the imaging lens 10, while the image side is in the positive direction A2 relative to the imaging lens 10.

[0026] Prism 7 includes an incident light surface 75, an exit light surface 76, and a reflecting surface 77. Lens 1 is disposed on the incident light side of prism 7, and lenses 2 to 6 are disposed on the exit light side of prism 7, with the optical axis I deflected on the reflecting surface 77 of prism 7. When light emitted from an object to be photographed on the object side enters the imaging lens 10, the light passing through lens 1 enters prism 7 from the incident light surface 75, is reflected on the reflecting surface 77, exits prism 7 from the exit light surface 76, and then sequentially passes through lenses 2, 3, 4, 5, 6, and filter 8, forming an image on the imaging surface 99. Filter 8 is, for example, an infrared cut-off filter, which allows light of appropriate wavelengths (e.g., infrared or visible light) to pass through while filtering out the desired infrared band.

[0027] The optical axis region of the object side 15 of lens 1 is convex and aspherical, while the image side 16 is planar and directly attached to the light-incident surface 75 of prism 7. In some embodiments, the total height of lens 1 and prism 7 in direction A1 is greater than or equal to 5 mm and less than or equal to 10 mm.

[0028] It should be noted that, compared to the case without lens 1, this embodiment, by arranging lens 1 with positive diopter on the light-incident side of prism 7, allows the imaging lens 10 to have a larger field of view and a larger effective focal length, and increases the amount of light entering the imaging lens 10. Furthermore, because the light is converged by lens 1 before entering prism 7, the diameters of lenses 2 to 6 can be reduced. Specifically, in some embodiments, the diameters of lenses 2, 3, 4, 5, and 6 are greater than or equal to 4 mm and less than or equal to 8.5 mm, thereby reducing the size of the imaging lens 10, lowering its weight, manufacturing difficulty, and manufacturing cost.

[0029] Lens 2 has positive refractive power. Its object side 25 has a convex optical axis region and its image side 26 has a concave optical axis region. Both the object side 25 and the image side 26 are aspherical.

[0030] Lens 3 has negative refractive power. Its object side 35 has a convex optical axis region, and its image side 36 has a concave optical axis region. Both the object side 35 and the image side 36 are aspherical.

[0031] Lens 4 has positive refractive power. Its object side 45 has a convex optical axis region and its image side 46 has a concave optical axis region. Both the object side 45 and the image side 46 are aspherical.

[0032] Lens 5 has positive refractive power. Its object side 55 has a convex optical axis region, and its image side 56 has a concave optical axis region. Both the object side 55 and the image side 56 are aspherical.

[0033] Lens 6 has negative refractive power. Its object-side surface 65 has a concave optical axis region, while its image-side surface 66 has a convex optical axis region. Both object-side surface 65 and image-side surface 66 are aspherical. Lens 6 moves during focusing by the imaging lens 10, with a movement distance of less than 1.5 mm. Conversely, lenses 2, 3, 4, and 5 form a fixed lens group that does not move during focusing by the imaging lens 10; the refractive power of this fixed lens group is positive.

[0034] Please refer to the following at the same time. Figure 1A as well as Figure 2A ,in Figure 2A A schematic diagram of the imaging lens in a second focusing state according to a first embodiment of the present invention is shown. Specifically, Figure 1A as well as Figure 2A These are schematic diagrams of the optical system when the image-taking lens 10 is focused at infinity (i.e., the first focusing state) and at 80 cm (i.e., the second focusing state). When the image-taking lens is focused at infinity, the distance between the object-side surface 15 of lens 1 and the image-side surface 66 of lens 6 on the optical axis I is minimized.

[0035] Other detailed optical data of the first embodiment are shown in Table 1. The field of view of the imaging lens 10 is 3.584 mm, the effective focal length (EFL) is 19.9 mm, and the aperture value is 2.6.

[0036] Table 1:

[0037]

[0038] In Table 1, the radius of curvature refers to the radius of curvature of each lens in the optical axis region. The spacing of the object-side surfaces 15 (1.000 mm as shown in Table 1) is the thickness of lens 1 on optical axis I. Since lens 1 is directly attached to the light-incident surface 75 of prism 7, the spacing of the image-side surfaces 16 is marked as 0.00 mm. The spacing of the light-incident surfaces 75 of prism 7 (7.650 mm as shown in Table 1) is the total length of optical axis I inside prism 7 in direction A1 and direction A2. The spacing of the light-exiting surfaces 76 (1.243 mm as shown in Table 1) is the distance between the light-exiting surface 76 of prism 7 and the object-side surface 25 of lens 2 on optical axis I, which is the gap between prism 7 and lens 2 on optical axis I, and so on. The spacing of aperture 0 (as shown in Table 1, -0.500 mm) represents the position of aperture 0 on optical axis I, which is 0.500 mm from the image side relative to the object side 25 of lens 2.

[0039] When the imaging lens 10 is focused at infinity (i.e., in the first focusing state, Z1 in Table 1 is infinity), then Z2 is 1.200 mm and Z3 is 1.309 mm, corresponding to... Figure 1A The optical architecture is shown. When the imaging lens 10 is focused at 80 cm (i.e., the second focusing state, Z1 in Table 1 is 800 mm), then Z2 is 2.409 mm and Z3 is 0.100 mm, corresponding to... Figure 2A The optical architecture shown.

[0040] As shown in Table 1, Figure 1A as well as Figure 2A As shown, in the first embodiment, lenses 2, 4, and 5 are positive meniscus lenses with their convex surfaces facing prism 7. Lens 3 is a negative meniscus lens with its convex surface facing prism 7. Lens 6 is a negative meniscus lens with its convex surface facing imaging plane 99.

[0041] In this embodiment, the object surfaces 15, 25, 35, 45, 55, and 65 of lenses 1, 2, 3, 4, 5, and 6, and the image surfaces 26, 36, 46, 56, and 66 of lenses 2, 3, 4, 5, and 6 are all aspherical surfaces, and these aspherical surfaces are defined according to the following formula (1):

[0042] (1)

[0043] Y: The distance between a point on the aspherical curve and the optical axis;

[0044] Z: Aspherical depth, which is the perpendicular distance between a point on the aspherical surface that is a distance Y from the optical axis and the tangent plane that is tangent to the vertex on the optical axis of the aspherical surface;

[0045] R: Radius of curvature of the lens surface;

[0046] K: Conic coefficient;

[0047] a 2i : The second-order aspherical coefficient.

[0048] In this embodiment, the conic coefficient K and various aspherical coefficients in the above aspherical formula (1) are shown in Table 2. In Table 2, number 15 represents the aspherical coefficient of the object side 15 of lens 1, number 25 represents the aspherical coefficient of the object side 25 of lens 2, number 26 represents the aspherical coefficient of the image side 26 of lens 2, and so on.

[0049] Table 2:

[0050]

[0051] See also Figures 1B to 1D , Figure 1B The graph shows the field curvature aberration in the meridional direction when light with wavelengths of 470 nm, 510 nm, 555 nm, 610 nm, and 650 nm is incident on the imaging lens 10 of the first embodiment in the first focusing state. Figure 1C The diagram shows the field curvature aberration in the sagittal direction when light with wavelengths of 470 nm, 510 nm, 555 nm, 610 nm, and 650 nm is incident on the imaging lens 10 of the first embodiment in the first focusing state. Figure 1D The graph shows the distortion curves when light with wavelengths of 470 nm, 510 nm, 555 nm, 610 nm and 650 nm is incident on the imaging lens 10 of the first embodiment in the first focusing state.

[0052] like Figure 1B as well as Figure 1C As shown in the field curvature aberration curve, the field curvature aberration of the five representative wavelengths falls within ±0.05 mm across the entire field of view, indicating that the imaging lens 10 of the first embodiment can effectively eliminate field curvature aberration in the first focusing state. Figure 1D As shown in the distortion curve, the distortion aberration of the five representative wavelengths is less than ±2% throughout the entire field of view, indicating that the imaging lens 10 of the first embodiment has good imaging quality in the first focusing state.

[0053] See also Figures 2B to 2D , Figure 2BThe graph shows the field curvature aberration in the meridional direction when light with wavelengths of 470 nm, 510 nm, 555 nm, 610 nm, and 650 nm is incident on the imaging lens 10 of the first embodiment in the second focusing state. Figure 2C The diagram shows the field curvature aberration in the sagittal direction when light with wavelengths of 470 nm, 510 nm, 555 nm, 610 nm, and 650 nm is incident on the imaging lens 10 of the first embodiment in the second focusing state. Figure 2D The graph shows the distortion curves when light with wavelengths of 470 nm, 510 nm, 555 nm, 610 nm and 650 nm is incident on the imaging lens 10 of the first embodiment in the second focusing state.

[0054] like Figure 2B as well as Figure 2C As shown in the field curvature aberration curve, the field curvature aberration of the five representative wavelengths falls within ±0.06 mm across the entire field of view, indicating that the imaging lens 10 of the first embodiment in the second focusing state can effectively eliminate field curvature aberration. Figure 2D As shown in the distortion curve, the distortion aberration of the five representative wavelengths is less than ±2% across the entire field of view, indicating that the imaging lens 10 of the first embodiment in the second focusing state has good imaging quality.

[0055] Reference Figure 3A This diagram illustrates the imaging lens in a first focusing state according to a second embodiment of the present invention. The imaging lens 20 is a periscope-type imaging lens, which sequentially includes a lens 1, a prism 7, a lens 2, a lens 3, a lens 4, a lens 5, a lens 6, and a filter 8 along the optical axis I from the object side to the image side. Each of the lenses 1, 2, 3, 4, 5, 6, and the filter 8 has an object-side surface 15, 25, 35, 45, 55, 65, 85 through which imaging light passes and an image-side surface 16, 26, 36, 46, 56, 66, 86 through which imaging light passes. The refractive powers of the lenses 1, 2, 3, 4, 5, and 6 are positive, positive, negative, positive, positive, and negative, respectively, and all lenses 1 to 6 are aspherical lenses. The object side described above is in the positive direction A1 relative to the imaging lens 20, while the image side is in the positive direction A2 relative to the imaging lens 20.

[0056] Prism 7 includes an incident light surface 75, an exit light surface 76, and a reflecting surface 77. Lens 1 is disposed on the incident light side of prism 7, and lenses 2 to 6 are disposed on the exit light side of prism 7, with the optical axis I deflected on the reflecting surface 77 of prism 7. When light emitted from an object to be photographed on the object side enters the imaging lens 20, the light passing through lens 1 enters prism 7 from the incident light surface 75, is reflected on the reflecting surface 77, exits prism 7 from the exit light surface 76, and then sequentially passes through lenses 2, 3, 4, 5, 6, and filter 8, forming an image on the imaging surface 99. Filter 8 is, for example, an infrared cut-off filter, which allows light of appropriate wavelengths (e.g., infrared or visible light) to pass through while filtering out the desired infrared band.

[0057] It should be noted that, compared to the case without lens 1, this embodiment, by arranging lens 1 with positive diopter on the light-incident side of prism 7, can enable the imaging lens 20 to have a larger field of view and increase the amount of light entering. Furthermore, because the light is converged by lens 1 before entering prism 7, the diameters of lenses 2 to 6 can be reduced, thereby reducing the size of the imaging lens 20, its weight, manufacturing difficulty, and manufacturing cost.

[0058] The optical axis region of the object side 15 of lens 1 is convex and aspherical, while the image side 16 is planar.

[0059] Lens 2 has positive refractive power. The optical axis region of its object side 25 is convex, and the optical axis region of its image side 26 is convex. Both the object side 25 and the image side 26 are aspherical.

[0060] Lens 3 has negative refractive power. The optical axis region of its object side 35 is concave, and the optical axis region of its image side 36 is concave. Both the object side 35 and the image side 36 are aspherical.

[0061] Lens 4 has positive refractive power. The optical axis region of its object side 45 is convex, and the optical axis region of its image side 46 is convex. Both the object side 45 and the image side 46 are aspherical.

[0062] Lens 5 has positive refractive power. The optical axis region of its object side 55 is convex, and the optical axis region of its image side 56 is convex. Both the object side 55 and the image side 56 are aspherical.

[0063] Lens 6 has negative refractive power. Its object-side surface 65 has a concave optical axis region, while its image-side surface 66 has a convex optical axis region. Both object-side surface 65 and image-side surface 66 are aspherical. Lens 6 moves during focusing by the imaging lens 20, with a movement distance less than or equal to 0.4 mm. Conversely, lenses 2, 3, 4, and 5 form a fixed lens group that does not move during focusing by the imaging lens 20, and the refractive power of this fixed lens group is positive.

[0064] Please refer to the following at the same time. Figure 3A as well as Figure 4A ,in Figure 4A A schematic diagram of the imaging lens in a second focusing state according to a second embodiment of the present invention is shown. Specifically, Figure 3A as well as Figure 4A These are schematic diagrams of the optical system when the image-taking lens 20 is focused at infinity (i.e., the first focusing state) and at 80 cm (i.e., the second focusing state). When the image-taking lens is focused at infinity, the distance between the object-side surface 15 of lens 1 and the image-side surface 66 of lens 6 on the optical axis I is minimized.

[0065] Other detailed optical data of the second embodiment are shown in Table 3. The field of view of the imaging lens 20 is 3.584 mm, the effective focal length (EFL) is 19.9 mm, and the aperture value is 2.6.

[0066] Table 3:

[0067]

[0068] In Table 3, the spacing of the object-side surfaces 15 (1.000 mm as shown in Table 3) represents the thickness of lens 1 on optical axis I. The spacing of the image-side surfaces 16 (0.100 mm as shown in Table 3) represents the gap between lens 1 and prism 7 on optical axis I. The spacing of the light-incident surfaces 75 of prism 7 (7.650 mm as shown in Table 3) represents the total length of optical axis I inside prism 7 in direction A1 and direction A2. The spacing of the light-excising surfaces 76 (3.000 mm as shown in Table 3) represents the distance between the light-excising surface 76 of prism 7 and the object-side surface 25 of lens 2 on optical axis I, which is the gap between prism 7 and lens 2 on optical axis I, and so on. The spacing of aperture 0 (-0.200 mm as shown in Table 3) represents the position of aperture 0 on optical axis I at 0.200 mm on the image side relative to the object-side surface 25 of lens 2.

[0069] When the imaging lens 20 is focused at infinity (i.e., in the first focusing state, Z1 in Table 3 is infinity), then Z2 is 2.234 mm and Z3 is 0.65 mm, corresponding to... Figure 3AThe optical architecture is shown. When the imaging lens 20 is focused at 80 cm (i.e., the second focusing state, Z1 in Table 3 is 800 mm), then Z2 is 2.634 mm and Z3 is 0.25 mm, corresponding to... Figure 4A The optical architecture shown.

[0070] As shown in Table 3, Figure 3A as well as Figure 4A As shown, lenses 2, 4, and 5 in the second embodiment are biconvex lenses. Lens 3 is a biconcave lens. Lens 6 is a negative meniscus lens with its convex surface facing the imaging plane 99.

[0071] In this embodiment, the object surfaces 15, 25, 35, 45, 55, and 65 of lenses 1, 2, 3, 4, 5, and 6, and the image surfaces 26, 36, 46, 56, and 66 of lenses 2, 3, 4, 5, and 6 are all aspherical surfaces, and these aspherical surfaces are defined according to the above formula (1).

[0072] In this embodiment, the conic coefficient K and various aspherical coefficients in the above aspherical formula (1) are shown in Table 4. In Table 4, number 15 represents the aspherical coefficient of the object side 15 of lens 1, number 25 represents the aspherical coefficient of the object side 25 of lens 2, number 26 represents the aspherical coefficient of the image side 26 of lens 2, and so on.

[0073] Table 4:

[0074]

[0075] See also Figures 3B to 3D , Figure 3B The graph shows the field curvature aberration in the meridional direction when light with wavelengths of 470 nm, 510 nm, 555 nm, 610 nm, and 650 nm is incident on the imaging lens 20 of the second embodiment in the first focusing state. Figure 3C The diagram shows the field curvature aberration curves in the sagittal direction when light with wavelengths of 470 nm, 510 nm, 555 nm, 610 nm, and 650 nm is incident on the imaging lens 20 of the second embodiment in the first focusing state. Figure 3D The graph shows the distortion curves when light with wavelengths of 470 nm, 510 nm, 555 nm, 610 nm and 650 nm is incident on the imaging lens 20 of the second embodiment in the first focusing state.

[0076] like Figure 3B as well as Figure 3CAs shown in the field curvature aberration curve, the field curvature aberration of the five representative wavelengths falls within ±0.03 mm across the entire field of view, indicating that the imaging lens 20 of the second embodiment can effectively eliminate field curvature aberration in the first focusing state. Figure 3D As shown in the distortion curve, the distortion aberration of the five representative wavelengths is less than ±2% across the entire field of view, indicating that the imaging lens 20 of the second embodiment has good imaging quality in the first focusing state.

[0077] See also Figures 4B to 4D , Figure 4B The graph shows the field curvature aberration in the meridional direction when light with wavelengths of 470 nm, 510 nm, 555 nm, 610 nm, and 650 nm is incident on the imaging lens 20 of the second embodiment in the second focusing state. Figure 4C The diagram shows the field curvature aberration in the sagittal direction when light with wavelengths of 470 nm, 510 nm, 555 nm, 610 nm, and 650 nm is incident on the imaging lens 20 of the second embodiment in the second focusing state. Figure 4D The graph shows the distortion curves when light with wavelengths of 470 nm, 510 nm, 555 nm, 610 nm and 650 nm is incident on the imaging lens 20 of the second embodiment in the second focusing state.

[0078] like Figure 4B as well as Figure 4C As shown in the field curvature aberration curve, the field curvature aberration of the five representative wavelengths falls within ±0.10 mm across the entire field of view, indicating that the imaging lens 20 of the second embodiment can effectively eliminate field curvature aberration in the second focusing state. Figure 4D As shown in the distortion curve, the distortion aberration of the five representative wavelengths is less than ±2% across the entire field of view, indicating that the imaging lens 20 of the second embodiment has good imaging quality in the second focusing state.

[0079] Based on the above, the imaging lens provided in this embodiment of the invention has a first lens disposed on the light-incident side of the prism to converge the light, and a second to a sixth lens disposed on the light-outcrystal side of the prism. The imaging lens can be used in smartphones and has a large effective focal length.

Claims

1. An image-capturing lens, characterized in that, The imaging lenses, arranged sequentially from the object side to the image side along the optical axis, include: First lens, prism, second lens, third lens, fourth lens, fifth lens, and sixth lens. The first lens has a convex object-side surface and a flat image-side surface; the second lens has a convex object-side surface; the third lens has a concave image-side surface; the fourth lens has a convex object-side surface; the fifth lens has a convex object-side surface; and the sixth lens has a concave object-side surface and a convex image-side surface. The first lens is disposed on the light-incident side of the prism, and the second to sixth lenses are disposed on the light-outceasing side of the prism, with the optical axis turning at the reflective surface of the prism. The imaging lens comprises six lenses with diopter, wherein the first to the sixth lenses are all aspherical lenses, and their diopter values ​​are positive, positive, negative, positive, positive, and negative, respectively. The ratio of the focal length of the first lens to the distance between the prism and the second lens on the optical axis is greater than or equal to 4 and less than or equal to 60. The second to fifth lenses form a fixed lens group, which does not move when the imaging lens is focusing, and its refractive power is positive. The sixth lens moves during focusing of the imaging lens, and the moving distance of the sixth lens is less than 1.5 mm. The diameter of the second lens to the sixth lens is greater than or equal to 4 mm and less than or equal to 8.5 mm.

2. The imaging lens according to claim 1, characterized in that, The refractive index of the sixth lens falls in the range of 1.6 to 1.

7.

3. The imaging lens according to claim 1, characterized in that, The Abbe number of the first lens falls within the range of 40 to 100.

4. The imaging lens according to claim 1, characterized in that, The ratio of the effective focal length to the aperture value of the imaging lens is greater than or equal to 7 and less than or equal to 8.

5. The imaging lens according to claim 1, characterized in that, The ratio of the radius of curvature of the object side of the first lens in the optical axis region to the refractive index of the first lens falls within the range of 5 to 15.

6. The imaging lens according to claim 1, characterized in that, The ratio of the focal length of the first lens to the distance between the prism and the second lens on the optical axis is greater than or equal to 5 and less than or equal to 25.

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