Imaging lens and camera device

Abstract

The problem is to realize a small, bright imaging lens and a camera device with stable optical performance. The solution is that the imaging lens of the camera device (1) has: a negative first lens (L1), a positive second lens (L2) with a concave-convex shape, an aperture stop (SP), a positive third lens (L3), and a positive combined lens composed of a positive fourth lens (L4) and a negative fifth lens (L5), and satisfies specific formulas related to the second and third lenses (L2, L3).

Description

Technical Field

[0001] This invention relates to imaging lenses and camera devices. Background Technology

[0002] Since the beginning of the year, portable imaging devices such as SLR cameras, mirrorless single-lens cameras, and digital cameras, as well as fixed imaging devices such as surveillance cameras and vehicle-mounted cameras, have become increasingly common. These imaging devices utilize solid-state imaging elements such as CCD (Charge Coupled Device) sensors or CMOS (Complementary Metal Oxide Semiconductor) sensors. Furthermore, the performance requirements for the imaging lenses used in these devices have increased due to the increasing pixel count of solid-state imaging elements.

[0003] Furthermore, in recent years, systems known as ADAS (Advanced Driver Assistance Systems) have become increasingly popular. These systems use in-vehicle cameras for sensing and provide appropriate driver assistance based on the analysis of the images obtained from the cameras. The imaging lenses used in these in-vehicle cameras also require small size and low cost, high image resolution, and minimal performance variation due to eccentric sensitivity.

[0004] In this imaging lens, an optical system is known to consist, from the object side to the image plane side, a negative lens with a concave shape facing the image plane side, a positive lens, a biconvex lens, and a combined lens having a positive combined optical power (see, for example, Patent Document 1). Additionally, in this imaging lens, an optical system is known to consist, from the object side to the image plane side, a negative lens with a concave shape facing the image plane side, a positive lens, a biconvex lens, a negative lens, and a positive lens (see, for example, Patent Document 2).

[0005] Prior art literature Patent documents Patent Document 1: Japanese Patent Application Publication No. 2009-75141 Patent Document 2: Japanese Patent Application Publication No. 2020-38401 Summary of the Invention The problem that the invention aims to solve In recent years, in order to support high resolution, bright optical systems with large aperture ratios are needed. When considering their application in automotive sensing camera devices, even brighter imaging lenses are required.

[0006] However, in the optical system disclosed in Patent Document 1, the F-value is around 2.0, which sometimes fails to ensure sufficient brightness. Furthermore, if the aperture ratio is increased in the optical system disclosed in Patent Document 1, the optical power configuration of each lens becomes inappropriate, making it difficult to ensure optical performance. Additionally, in the optical system disclosed in Patent Document 2, the optical power configuration of the lenses near the image plane is positive-negative-positive, resulting in high eccentricity sensitivity of each lens, making it difficult to adjust the lens arrangement and ensure stable optical performance. Therefore, in the prior art, there is still room for exploration regarding the realization of a small, bright imaging lens with stable optical performance.

[0007] One objective of the present invention is to realize a small, bright imaging lens and a camera device with stable optical performance.

[0008] Methods for solving problems To address the aforementioned issues, one embodiment of the present invention relates to an imaging lens comprising, from the object side to the image plane side, the following components in sequence: a first lens having negative optical power, a second lens with a concave-convex shape having positive optical power, an aperture stop, a third lens having positive optical power, and a combined lens having a positive combined optical power formed by combining a fourth lens having positive optical power and a fifth lens having negative optical power, wherein the imaging lens satisfies the following formula.

[0009] 0.825≤D23 / f≤1.850(1-1) 0.48≤L_D3 / f≤1.20 (1-2) in, D23: The interplane distance on the axis between the second lens and the third lens. f: Focal length of the imaging lens L_D3: Center thickness of the third lens In addition, in order to solve the above-mentioned problems, one aspect of the present invention relates to a camera device that includes the above-described imaging lens and an imaging element that converts the optical image formed by the imaging lens into an electrical signal on the image plane side of the imaging lens.

[0010] Invention Effects According to one aspect of the present invention, it is possible to realize a small, bright imaging lens and a camera device with stable optical performance. Attached Figure Description

[0011] Figure 1 This is a schematic diagram illustrating the lens structure of the imaging lens of Embodiment 1.

[0012] Figure 2 This is a diagram showing the longitudinal aberration of the imaging lens in Example 1.

[0013] Figure 3 This is a schematic diagram illustrating the lens structure of the imaging lens in Embodiment 2.

[0014] Figure 4 This is a diagram showing the longitudinal aberration of the imaging lens in Example 2.

[0015] Figure 5 This is a schematic diagram illustrating the lens structure of the imaging lens in Embodiment 3.

[0016] Figure 6 This is a diagram showing the longitudinal aberration of the imaging lens in Example 3.

[0017] Figure 7 This is a schematic diagram illustrating the lens structure of the imaging lens in Embodiment 4.

[0018] Figure 8 This is a diagram showing the longitudinal aberration of the imaging lens in Example 4.

[0019] Figure 9 This is a schematic diagram illustrating the lens structure of the imaging lens in Embodiment 5.

[0020] Figure 10 This is a diagram showing the longitudinal aberration of the imaging lens in Example 5.

[0021] Figure 11 This is a schematic diagram illustrating the lens structure of the imaging lens in Embodiment 6.

[0022] Figure 12 This is a diagram showing the longitudinal aberration of the imaging lens in Example 6.

[0023] Figure 13 This is a schematic diagram illustrating the structure of a camera device according to one embodiment of the present invention.

[0024] Explanation of reference numerals in the attached figures 1. Camera device 10 Lens tubes 20 main bodies L1~L5 First~Fifth Lenses SP aperture stop G Optical Module IP Image OA optical axis Detailed Implementation In the following description, "lens" does not include parallel plates and can refer to a single lens. Examples of single lenses include biconvex lenses, plano-convex lenses, convex-concave-convex lenses, and concave-concave-convex lenses. Lenses can be either spherical or aspherical. An aspherical lens means that at least one of its lens surfaces is aspherical. Examples of aspherical lenses include: composite lenses with a resin layer having an aspherical shape on at least one lens surface, and glass-molded aspherical lenses made of glass material where at least one lens surface is aspherical. Furthermore, "joined lens" means a construction in which two or more single lenses are integrally formed without air gaps.

[0025] In addition, in the following explanation, "optical power" will also be referred to as "power", a lens with positive optical power will also be referred to as a "positive lens", and a lens with negative optical power will also be referred to as a "negative lens".

[0026] [Imaging Lens] An imaging lens according to one embodiment of the present invention may have a structure comprising, from the object side to the image plane side, a first lens having negative optical power, a second lens with a concave-convex shape having positive optical power, an aperture stop, a third lens having positive optical power, a positive fourth lens having positive combined optical power, and a combined fifth lens, forming a combined lens. This structure is preferred from the viewpoint of achieving miniaturization and high-performance imaging in automotive cameras. From the aforementioned viewpoint, it is preferable that the imaging lens comprises only the first to fifth lenses described above.

[0027] [Optical Structure] <First Lens> The first lens has negative optical power. The first lens can be appropriately selected from known negative lenses.

[0028] <Second Lens> The second lens has a concave-convex shape and positive optical power. The second lens can be appropriately selected from known positive concave-convex lenses.

[0029] The second lens is preferably a positive concave-convex lens with its convex surface facing the image plane. By using such a positive concave-convex lens as the second lens, the principal point of the second lens can be positioned on the image plane side (rear) of the second lens. Therefore, the above structure is preferred from the viewpoint of ensuring space on the image plane side (rear) of the second lens.

[0030] <The Third Lens> The third lens has positive optical power. The third lens can be appropriately selected from known positive lenses.

[0031] <Joint Lens> The imaging lens of this embodiment has a combined lens, which is formed by joining a fourth lens having positive optical power and a fifth lens having negative optical power, and thus has a positive combined optical power. Having this combined lens is preferable from the viewpoint of effectively correcting aberrations generated in the first and second lenses. Furthermore, to shorten the overall length of the imaging lens, it is preferable to have fewer lens elements; having this combined lens is also preferable from the viewpoint of miniaturizing the imaging lens. In this way, having this combined lens is suitable even with significant limitations on diameter and overall length, particularly from the viewpoint of effectively maintaining spherical aberration correction and chromatic aberration correction, and is preferable from the viewpoint of achieving an imaging lens with good performance in all aberrations.

[0032] The fourth lens has positive optical power. The positive optical power of the fourth lens can be suitably determined within the range where the combined lens has positive combined optical power when it forms a combined lens with the fifth lens. The fourth lens can be suitably selected from known positive lenses, within the range that allows it to form a combined lens with the fifth lens.

[0033] The fifth lens has a negative optical power. The negative optical power of the fifth lens can be suitably determined within a range where, when combined with the fourth lens, the combined lens has a positive combined optical power. The fifth lens can be suitably selected from known negative lenses, within a range that can form a combined lens with the fourth lens.

[0034] <Aperture Stop> An aperture stop is positioned between the second and third lenses. The aperture stop's position simply needs to be within the optical path between the second and third lenses; regardless of its exact location, sufficient brightness and optical performance of the imaging lens can be achieved. The position of the aperture stop can be determined, for example, by the structure of the lens barrel housing the imaging lens.

[0035] <Other Optical Components> In addition to the lens and aperture stop described above, the imaging lens of this embodiment may include other optical elements besides the lens, within the scope that can achieve the effects of the present invention. Examples of other optical elements include filters, phase plates, crystal low-pass filters, and infrared cut-off filters. For example, when the imaging lens includes the above-mentioned filter type between the final lens and the image plane, it is preferable from the viewpoint of reducing the diameter of the entire lens system.

[0036] Furthermore, it is preferable from the viewpoint of obtaining the optical effects of the second and third lenses when there is an air gap between the second and third lenses. However, other optical elements other than lenses may also be interposed between the second and third lenses.

[0037] [Optical Properties] When the imaging lens of this embodiment satisfies at least one of the formulas described below, it is preferred from the viewpoint of realizing an imaging lens that is small, bright and has stable optical performance.

[0038] <Equation (1-1)> 0.825≤D23 / f≤1.850(1-1) in, D23: The interplane distance on the axis between the second and third lenses. f: Focal length of the imaging lens Equation (1-1) relates to the ratio of the distance between the second and third lenses to the focal length of the imaging lens. Furthermore, D23 is the equivalent air length. If D23 / f exceeds 1.850, the diameter of the beam incident on the third lens increases, tending to increase the diameter of the third lens and lenses closer to the image plane. Therefore, the imaging lens becomes larger in both radial and longitudinal directions, making miniaturization difficult. Additionally, if the imaging lens is a bright lens with a small F-number, the increased beam diameter leads to increased spherical aberration, sometimes making it difficult to correct aberrations throughout the entire imaging lens. If D23 / f is less than 0.825, the distance between the front group (first and second lenses) and the rear group (third to fifth lenses) is too close, making it difficult to effectively correct chromatic aberration and distortion aberrations generated in the front group within the rear group. Furthermore, the increased optical power of the rear group to correct aberrations causes increased eccentricity sensitivity, making it difficult to adjust the arrangement of the lenses in the imaging lens and ensuring good optical performance.

[0039] From the viewpoint of miniaturization and good aberration correction, D23 / f is more preferably 1.750 or less, and even more preferably 1.200 or less. Furthermore, from the viewpoint of good aberration correction and good optical performance assurance, D23 / f is more preferably 1.000 or more, and even more preferably 1.200 or more.

[0040] <Equation (1-2)> 0.48≤L_D3 / f≤1.20 (1-2) in, L_D3: Center thickness of the third lens f: Focal length of the imaging lens Equation (1-2) relates to the ratio of the center thickness of the third lens to the focal length of the imaging lens. If L_D3 / f exceeds 1.20, the wall thickness of the third lens increases, leading to increased axial chromatic aberration. This makes it difficult to ensure the optical performance of a bright imaging lens with a small F-number. Furthermore, the overall length of the imaging lens increases, which is undesirable from a miniaturization perspective. If L_D3 / f is less than 0.48, the eccentricity sensitivity increases, making it difficult to adjust the arrangement of the individual lenses in the imaging lens and ensuring good optical performance. Consequently, it becomes difficult to ensure the necessary manufacturing edges, making it undesirable from a production efficiency perspective.

[0041] From the viewpoint of ensuring optical performance and axial miniaturization, L_D3 / f is more preferably 1.10 or less, and even more preferably 1.00 or less. Furthermore, from the viewpoint of suppressing changes in optical characteristics caused by variations in eccentricity sensitivity and from the viewpoint of productivity, L_D3 / f is more preferably 0.53 or more, and even more preferably 0.55 or more.

[0042] <Formula (2)> -0.120≤f_L1 / f_L45≤-0.010 (2) in, f_L1: Focal length of the first lens f_L45: Focal length of the coupled lens Equation (2) relates to an appropriate ratio of the optical power of the first lens to the optical power of the joint lens. When the imaging lens satisfies Equation (2), it is preferable from the viewpoint of achieving good correction of various aberrations and miniaturization of the imaging lens. If f_L1 / f_L45 is less than -0.120, the aberrations generated by the fourth and fifth lenses increase, and astigmatism, coma, and chromatic aberration at magnification sometimes worsen. If f_L1 / f_L45 exceeds -0.010, the aberrations generated by the first lens increase, and coma sometimes worsens.

[0043] From the viewpoint of effectively correcting aberrations, f_L1 / f_L45 is more preferably -0.090 or higher, and even more preferably -0.080 or higher. Furthermore, from the viewpoint of effectively correcting coma, f_L1 / f_L45 is more preferably -0.015 or lower.

[0044] <Formula (3)> 0.180≤f_L3 / f_L2≤0.600 (3) in, f_L2: Focal length of the second lens f_L3: Focal length of the third lens Equation (3) relates to the ratio of the focal length of the second lens to the focal length of the third lens. If f_L3 / f_L2 is less than 0.180, the error sensitivity corresponding to the eccentricity of the third lens relative to the optical axis tends to increase. If f_L3 / f_L2 exceeds 0.600, coma and astigmatism tend to occur, or coma and astigmatism tend to increase.

[0045] From the viewpoint of suppressing changes in optical properties caused by variations in eccentricity sensitivity, f_L3 / f_L2 is more preferably 0.200 or more, and even more preferably 0.250 or more. Furthermore, from the viewpoint of suppressing aberrations, f_L3 / f_L2 is more preferably 0.550 or less, and even more preferably 0.450 or less.

[0046] <Formula (4)> 4.00≤f_L2 / f≤10.00(4) in, f_L2: Focal length of the second lens f: Focal length of the imaging lens Equation (4) relates to the appropriate ratio of the positive optical power of the second lens to the optical power of the imaging lens. When the imaging lens satisfies Equation (4), it is preferable from the viewpoint of achieving good correction of various aberrations in the imaging lens and miniaturization. If f_L² / f is less than 4.00, the positive optical power of the second lens is too strong, sometimes resulting in coma and astigmatism. If f_L² / f exceeds 10.00, the positive optical power of the second lens is too weak, making it difficult to shorten the overall length of the imaging lens.

[0047] From the viewpoint of suppressing aberrations, f_L2 / f is more preferably 4.50 or higher, and even more preferably 5.00 or higher. Furthermore, from the viewpoint of miniaturizing the imaging lens along its axis, f_L2 / f is more preferably 9.50 or lower, and even more preferably 8.50 or lower.

[0048] <Formula (5)> -1.00≤f_L1 / f_L3≤-0.30(5) in, f_L1: Focal length of the first lens f_L3: Focal length of the third lens Equation (5) relates to the ratio of the focal length of the first lens to the focal length of the third lens. If f_L1 / f_L3 is less than -1.00, the image plane tilts downwards, sometimes resulting in an out-of-focus image in the center and periphery of the image. If f_L1 / f_L3 exceeds -0.30, the image plane tilts upwards, still sometimes resulting in an out-of-focus image in the center and periphery of the image.

[0049] From the viewpoint of suppressing image plane downward tilt, f_L1 / f_L3 is more preferably -0.95 or more, and even more preferably -0.85 or more. Furthermore, from the viewpoint of suppressing image plane upward tilt, f_L1 / f_L3 is more preferably -0.40 or less, and even more preferably -0.50 or less.

[0050] <Formula (6)> 0.010≤f_L3 / f_L45≤0.150(6) in, f_L3: Focal length of the third lens f_L45: Focal length of the coupled lens Equation (6) relates to the ratio of the focal length of the third lens to the combined focal length in the joint lens of the fourth and fifth lenses. The third lens preferably has a positive optical power that is primarily related to imaging. Therefore, the ratio of the focal lengths of the third lens and the joint lens is preferably set such that it can effectively correct for spherical aberration and coma while taking into account the miniaturization of the imaging lens axis or ensuring back focus.

[0051] If f_L3 / f_L45 is less than 0.010, the back focal length of the imaging lens is too short, sometimes making it impossible to mount or fully correct spherical aberration caused by the third lens. If f_L3 / f_L45 exceeds 0.150, the overall length of the imaging lens is sometimes too large, or coma caused by the joining lenses cannot be fully corrected.

[0052] From the perspective of both sizing capability and effective aberration correction, f_L3 / f_L45 is more preferably 0.012 or higher. More preferably, it is 0.015 or higher. Furthermore, from the perspective of miniaturization of the imaging lens axis and effective spherical aberration correction, f_L3 / f_L45 is more preferably 0.012 or higher, more preferably 0.015 or higher. More preferably, it is 0.125 or lower, and even more preferably 0.098 or lower.

[0053] <Formula (7)> -3.00<G45L1SF<-1.20(7) Equation (7) relates to the shape (shape factor) of the joining lens. In Equation (7), “G45L1SF” is represented by Equation (7-1).

[0054] G45L1SF=(G4L1Lr+G5L1Rr) / (G4L1Lr-G5L1Rr)(7-1) In equation (7-1), "G4L1Lr" is the radius of curvature of the object-side lens surface of the fourth lens, and "G5L1Rr" is the radius of curvature of the image-side lens surface of the fifth lens. When the imaging lens satisfies equation (7), it is preferred from the viewpoint of effectively correcting magnification chromatic aberration and coma.

[0055] If the G45L1SF value is below -3.00, the radius of curvature of the fourth lens is too large, resulting in insufficient optical power and sometimes an increased overall lens length. Additionally, the radius of curvature of the fifth lens is too small, sometimes leading to over-correction of coma and astigmatism. If the G45L1SF value is above -1.20, the radius of curvature of the fourth lens is too small, sometimes resulting in insufficient correction of spherical aberration and coma. Additionally, the radius of curvature of the fifth lens is too large, sometimes resulting in insufficient correction of coma and astigmatism.

[0056] From the viewpoint of miniaturizing the imaging lens along its axis and effectively correcting coma and astigmatism, the G45L1SF is more preferably -2.50 or higher. Furthermore, from the viewpoint of effectively correcting spherical aberration and coma, the G45L1SF is more preferably -1.40 or lower, and even more preferably -1.50 or lower.

[0057] <Formula (8)> -3.00≤f_L1 / f≤-1.00 (8) in, f_L1: Focal length of the first lens f: Focal length of the imaging lens Equation (8) relates to the appropriate ratio of the optical power of the first lens to the optical power of the imaging lens. When the imaging lens satisfies Equation (8), it is preferred from the viewpoint of effectively correcting the various aberrations of the imaging lens and achieving a small imaging lens with a large depth of field.

[0058] If f_L1 / f is less than -3.00, the negative optical focal length of the first lens is too weak, making it difficult to shorten the overall length of the imaging lens. If f_L1 / f exceeds -1.00, the negative optical focal length of the first lens is too strong, easily causing coma and astigmatism, or making coma and astigmatism more pronounced. Furthermore, if f_L1 / f exceeds -1.00, the radius of curvature of the lens surface on the image plane side of the first lens is too small, thus the error sensitivity corresponding to the eccentricity of the first lens relative to the optical axis is more likely to increase.

[0059] From the viewpoint of miniaturizing the imaging lens along its axis, f_L1 / f is more preferably -2.50 or higher, and even more preferably -1.74 or higher. Furthermore, from the viewpoint of suppressing coma and astigmatism, and suppressing changes in optical characteristics caused by variations in eccentric sensitivity, f_L1 / f is more preferably -1.10 or lower, and even more preferably -1.20 or lower.

[0060] <Formula (9)> -0.400≤f_L1 / f_L2≤-0.200 (9) in, f_L1: Focal length of the first lens f_L2: Focal length of the second lens Equation (9) relates to the appropriate ratio of the optical power of the first lens to the optical power of the second lens. When the imaging lens satisfies Equation (9), it is preferred from the viewpoints of well correcting various aberrations and miniaturizing the imaging lens.

[0061] If f_L1 / f_L2 is less than -0.400, the optical focal length of the first lens is too weak, and the height of the light rays incident on the first lens sometimes increases, resulting in a larger diameter for the first lens. Furthermore, if f_L1 / f_L2 is less than -0.400, the optical focal length of the second lens is too strong, thus its performance against eccentricity is insufficient, sometimes making it difficult to ensure the desired optical characteristics of the imaging lens. Additionally, if f_L1 / f_L2 exceeds -0.200, the optical focal length of the first lens is too strong, thus shifting the focal position of the first lens towards the image plane. As a result, the overall length of the imaging device sometimes increases. Moreover, if f_L1 / f_L2 exceeds -0.200, the Purzval increases, and field curvature correction sometimes becomes excessive.

[0062] From the viewpoint of miniaturizing the imaging lens in the radial direction and ensuring optical characteristics, f_L1 / f_L2 is more preferably -0.350 or higher, and even more preferably -0.300 or higher. Furthermore, from the viewpoint of miniaturizing the imaging lens in the axial direction and effectively correcting field curvature, f_L1 / f_L2 is more preferably -0.205 or lower.

[0063] <Formula (10)> 1.00 < G1L1SF < 3.00 (10) Equation (10) relates to the shape (shape factor) of the first lens. In Equation (10), “G1L1SF” is represented by Equation (10-1).

[0064] G1L1SF=(G1L1Lr+G1L1Rr) / (G1L1Lr-G1L1Rr)(10-1) In equation (10-1), “G1L1Lr” is the radius of curvature of the object-side lens surface of the first lens, and “G1L1Rr” is the radius of curvature of the image-side lens surface of the first lens. When the imaging lens satisfies equation (10), it is preferred from the viewpoint of effectively correcting non-point chromatic aberration and distortion aberration.

[0065] If G1L1SF is below 1.00, the radius of curvature of the first lens is too large and the optical power of the first lens is sometimes insufficient, resulting in a larger overall length of the imaging lens.

[0066] If G1L1SF is above 3.00, the radius of curvature of the first lens is too small, and the correction of astigmatism and aberration is sometimes insufficient.

[0067] From the viewpoint of effectively correcting astigmatism and distortion aberrations, G1L1SF is more preferably 2.70 or less, and even more preferably 2.10 or less.

[0068] <Formula (11)> 0.500≤D23 / BF≤1.000(11) in, D23: The interplane distance on the axis between the second and third lenses. BF: Back focal length of the imaging lens Equation (11) relates to the ratio of the interplane distance on the axis between the second lens and the third lens to the back focal length of the imaging lens. The "back focal length" is the air-converted value of the distance from the lens surface on the image plane side of the fifth lens to the paraxial image plane. In addition, D23 is also the air-converted length.

[0069] If D23 / BF exceeds 1.000, the spacing between the second and third lenses becomes too large, sometimes increasing the overall length of the imaging lens. Additionally, the height of the light rays incident on the third lens increases, making it sometimes difficult to correct spherical aberration. If D23 / BF is less than 0.500, the back focal length becomes too large, sometimes increasing the overall length of the imaging lens.

[0070] From the viewpoint of miniaturizing the imaging lens along its axis and effectively correcting spherical aberration, a D23 / BF ratio of 0.900 or less is more preferred, and 0.850 or less is even more preferred. Furthermore, from the viewpoint of miniaturizing the imaging lens along its axis, a D23 / BF ratio of 0.600 or more is more preferred, and 0.700 or more is even more preferred.

[0071] [Camera device] One embodiment of the present invention relates to a camera device having the optical system described above in this embodiment. Figure 13 The structure of the camera device in this embodiment is schematically shown. For example... Figure 13 As shown, the camera device 1 has a main body 20 and a lens barrel 10. The camera device 1 is, for example, a vehicle-mounted camera device.

[0072] The main body 20 has an imaging element and a protective glass CG. The imaging element is a photoelectric conversion element that converts an optical image into an electrical signal, such as a solid-state imaging element. Examples of solid-state imaging elements include CCD (Charge-Coupled Device) sensors and CMOS (Complementary Metal Oxide Semiconductor) sensors. Furthermore, the label IP represents the surface (image plane) of the imaging element.

[0073] The lens barrel 10 is detachably mounted to the main body 20. Inside it, a first lens L1, a second lens L2, a third lens L3, and a combined lens of a fourth lens L4 and a fifth lens L5 are sequentially arranged along the optical axis OA. The first lens L1 to the fifth lens L5 constitute the imaging lens of this embodiment described above. Furthermore, the optical axis OA is the optical axis common to all the lenses of the lens barrel 10 and the imaging element of the main body 20.

[0074] In the imaging device 1, light incident from the object side of the imaging lens of this embodiment is ultimately imaged on the imaging surface of the imaging element. Then, the imaging element performs photoelectric conversion on the light received as an image and outputs it as an electrical signal, generating a digital image corresponding to the image of the subject. The digital image can be recorded, for example, on a recording medium such as an HDD (Hard Disk Device) or a memory card, optical disc, or magnetic tape. Furthermore, when the imaging device 1 is a silver halide thin-film camera, the image plane IP corresponds to the thin-film surface.

[0075] Since the imaging device 1 has the small, bright, and stable optical performance of the imaging lens of this embodiment described above, it achieves the same effect in the imaging device. Therefore, the imaging device 1 can be applied to fixed imaging devices such as surveillance cameras and vehicle-mounted cameras.

[0076] 〔Summarize〕 The first aspect of the present invention is an imaging lens comprising, from the object side to the image plane side, the following components in sequence: a first lens (L1) having negative optical power; a second lens (L2) with a concave-convex shape having positive optical power; an aperture stop (SP); a third lens (L3) having positive optical power; and a combined lens having a positive combined optical power formed by joining a fourth lens (L4) having positive optical power and a fifth lens (L5) having negative optical power, wherein the imaging lens satisfies the above-described equations (1-1) and (1-2). According to the first aspect, a small, bright imaging lens with stable optical performance can be realized.

[0077] The second aspect of the present invention satisfies equation (2) above, as in the first aspect. The second aspect is more effective from the viewpoint of better correcting aberrations.

[0078] The third aspect of the present invention satisfies equation (3) above, as in the first or second aspect. The third aspect is more effective from the viewpoints of suppressing changes in optical properties caused by changes in eccentricity sensitivity and suppressing the generation of aberrations.

[0079] The fourth aspect of the present invention satisfies equation (4) above in any of the first to third aspects. The fourth aspect is more effective from the viewpoints of suppressing aberrations and miniaturizing the imaging lens along its axis.

[0080] The fifth aspect of the present invention satisfies equation (5) above in any one of the first to fourth aspects. The fifth aspect is more effective from the viewpoint of suppressing image plane tilt.

[0081] The sixth aspect of the present invention satisfies equation (6) above in any of the first to fifth aspects. The sixth aspect is more effective from the viewpoints of well correcting aberrations, miniaturizing the axial direction of the imaging lens, and well correcting spherical aberration.

[0082] The seventh aspect of the present invention satisfies equation (7) above in any one of the first to sixth aspects. The seventh aspect is more effective from the viewpoints of miniaturizing the imaging lens along its axis and effectively correcting coma and astigmatism.

[0083] The eighth aspect of the present invention satisfies equation (8) above in any one of the first to seventh aspects. The eighth aspect is more effective from the viewpoints of miniaturizing the imaging lens axis, suppressing coma and astigmatism, and suppressing changes in optical characteristics caused by changes in eccentric sensitivity.

[0084] The ninth aspect of the present invention satisfies equation (9) above in any one of the first to eighth aspects. The ninth aspect is more effective from the viewpoints of radial miniaturization of the imaging lens, ensuring optical characteristics, and better correction of field curvature.

[0085] The tenth aspect of the present invention satisfies equation (10) above in any one of the first to ninth aspects. The tenth aspect is more effective from the viewpoint of better correcting astigmatism and distortion aberrations.

[0086] The eleventh aspect of the present invention is a camera device (1) comprising an imaging lens according to any one of the first to tenth aspects, and an imaging element that converts the optical image formed by the imaging lens into an electrical signal on the image plane side of the imaging lens. According to the eleventh aspect, a small, bright camera device with stable optical performance can be realized.

[0087] Based on the above description, it can be determined that the imaging lens of the present invention achieves low cost and miniaturization with a smaller number of lens elements, and is capable of high-resolution imaging. Furthermore, the imaging device of the present invention, due to having the aforementioned imaging lens, achieves miniaturization and is also capable of high-resolution imaging.

[0088] In this way, the present invention can provide an imaging lens that, while miniaturizing the overall imaging lens, especially the diameter of the lens located on the object side and the overall length of the imaging lens, can achieve good imaging performance with a bright F-value of about 1.6 and is not easily affected by eccentricity.

[0089] The imaging lens and camera device of the present invention are particularly suitable for surveillance cameras, anti-theft cameras, or vehicle-mounted cameras installed indoors or outdoors.

[0090] The imaging lens involved in this invention is small, bright, and has stable optical performance. This invention has the effect of, for example, expected to contribute to achieving the United Nations Sustainable Development Goal (SDGs) Goal 9, "Industry, Innovation and Infrastructure".

[0091] This invention is not limited to the embodiments described above, and various modifications can be made within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included within the technical scope of this invention.

[0092] [Example] The following describes one embodiment of the present invention.

[0093] The lens structure in the imaging lens of the embodiment of the present invention is as follows: Figure 1 , 3 As shown in Figures 5, 7, 9, and 11, the imaging lens of an embodiment of the present invention is composed of a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, and a fifth lens L5, sequentially from the object side to the image plane side. The fourth lens L4 and the fifth lens L5 constitute a combined lens. An optical aperture stop SP is disposed between the second lens L2 and the third lens L3. The aperture stop SP limits the diameter (light intensity) of the light beam incident from the object side to the image plane IP side. An optical module G is disposed between the fifth lens L5 and the image plane IP. The optical module G is equivalent to a filter, a phase plate, a crystal low-pass filter, or an infrared cutoff filter, etc. In an imaging device equipped with this imaging lens and a solid-state imaging element, the image plane IP is equivalent to the imaging surface of the solid-state imaging element. As a solid-state imaging element, photoelectric conversion elements such as CCD (charge-coupled device) sensors or CMOS (complementary metal-oxide-semiconductor) sensors can be used, for example.

[0094] The longitudinal aberration diagram of the imaging lens in an embodiment of the present invention is as follows: Figure 2 , 4As shown in Figures 6, 8, 10, and 12. The longitudinal aberration diagrams of each embodiment, from left to right relative to the paper, sequentially represent spherical aberration (SA [mm]), astigmatism (AST [mm]), and distortion aberration (DIS [%)). In the spherical aberration diagram, the vertical axis represents the F-value (Fno), the dashed line represents the spherical aberration at the d-line (wavelength 587.56 nm), the dotted line represents the spherical aberration at the C-line (wavelength 656.27 nm), and the solid line represents the spherical aberration at the g-line (wavelength 435.84 nm). In the astigmatism diagram, the vertical axis represents the image height (Y), the dashed line represents the astigmatism of the sagittal ray ΔS at the d-line (wavelength 587.56 nm), and the three-dotted line represents the astigmatism of the meridional ray ΔT. In the distortion aberration diagram, the vertical axis represents the image height (Y), and the dashed line represents the distortion aberration (distortion) at the d-line (wavelength 587.56 nm).

[0095] The surface data of all lenses in the imaging lens of the embodiments of the present invention are shown in Tables 1, 4, 7, 10, 13, and 16. In these tables, the "surface number" is the first lens surface located on the object side among the lenses constituting the imaging lens, and indicates the number of the lens surfaces that increase sequentially towards the image plane. "R" shown in the table indicates the radius of curvature [mm] of the lens surface corresponding to each surface number. Among them, a surface with a value of INF for R indicates that the surface is a plane. "D" shown in the table indicates the axial surface interval [mm] between the lens surface with surface number i (i is set to a natural number) and the lens surface with surface number i+1. "Nd" shown in the table indicates the refractive index at the d-line (wavelength 587.56nm) of each lens. "ABV" shown in the table indicates the Abbe number of each lens based on the d-line (wavelength 587.56nm).

[0096] The surface data of the aspherical lens in the imaging lens of the embodiments of the present invention are shown in Tables 2, 5, 8, 11, 14, and 17. In these tables, the surface number of the lens that is set as an aspherical surface and its aspherical coefficient are indicated. Furthermore, the aspherical shape can be represented by the following aspherical formula when the optical axis direction is shifted by z at a position set at a distance h from the optical axis with respect to the surface vertex.

[0097] z = ch 2 / [1+{1-(1+k)c 2 h 2} 1 / 2 ]+A4h 4 +A6h 6 +A8h 8 +A10h 10 ··· in, c: Curvature (1 / r) h: Height from the optical axis k: Conic coefficient (conic constant) A4, A6, A8, A10...: Aspheric coefficients for each degree Furthermore, the notation "E±m" (where m represents an integer) in the values ​​of the aspheric coefficient and the conic constant signifies "×10". ±m ".

[0098] Various specifications of the imaging lens in embodiments of the present invention are shown in Tables 3, 6, 9, 12, 15, and 18. These tables represent the focal length [mm], F-number (Fno), half field of view (θ) [deg], image height [mm], total lens length [mm], and back focal length (BF) of the entire imaging lens system. Furthermore, "total lens length" is the sum of the distance from the object-side surface of the first lens to the image-side surface of the fifth lens and the back focal length (BF). Additionally, the back focal length (BF) is a value obtained by converting the distance from the image-side surface of the fifth lens to the paraxial image plane using air.

[0099] [Example 1] Figure 1 This illustrates the lens structure of the imaging lens in Embodiment 1. Additionally, Figure 2 The longitudinal aberration of the imaging lens in Example 1 is shown. Furthermore, Tables 1 to 3 respectively show the surface data, aspherical data, and various specifications of the imaging lens in Example 1.

[0100] [Table 1]

[0101] [Table 2]

[0102] [Table 3]

[0103] [Example 2] Figure 3 This illustrates the lens structure of the imaging lens in Example 2. Additionally, Figure 4 The longitudinal aberration of the imaging lens in Example 2 is shown. Furthermore, Tables 4 to 6 respectively show the surface data, aspherical data, and various specifications of the imaging lens in Example 2.

[0104] [Table 4]

[0105] [Table 5]

[0106] [Table 6]

[0107] [Example 3] Figure 5 This illustrates the lens structure of the imaging lens in Example 3. Additionally, Figure 6 The longitudinal aberration of the imaging lens in Example 3 is shown. Furthermore, Tables 7 to 9 respectively show the surface data, aspherical data, and various specifications of the imaging lens in Example 3.

[0108] [Table 7]

[0109] [Table 8]

[0110] [Table 9]

[0111] [Example 4] Figure 7 This illustrates the lens structure of the imaging lens in Example 4. Additionally, Figure 8 The longitudinal aberration of the imaging lens in Example 4 is shown. Furthermore, Tables 10 to 12 respectively show the surface data, aspherical data, and various specifications of the imaging lens in Example 4.

[0112] [Table 10]

[0113] [Table 11]

[0114] [Table 12]

[0115] [Example 5] Figure 9 This illustrates the lens structure of the imaging lens in Example 5. Additionally, Figure 10 The longitudinal aberration of the imaging lens in Example 5 is shown. Furthermore, Tables 13 to 15 respectively show the surface data, aspherical data, and various specifications of the imaging lens in Example 5.

[0116] [Table 13]

[0117] [Table 14]

[0118] [Table 15]

[0119] [Example 6] Figure 11 This illustrates the lens structure of the imaging lens in Example 6. Additionally, Figure 12The longitudinal aberration of the imaging lens in Example 6 is shown. Furthermore, Tables 16 to 18 respectively show the surface data, aspherical data, and various specifications of the imaging lens in Example 6.

[0120] [Table 16]

[0121] [Table 17]

[0122] [Table 18]

[0123] Table 19 shows the calculated values ​​of the formulas described above in Examples 1 to 6.

[0124] [Table 19]

Claims

1. An imaging lens, comprising, from the object side to the image plane side, the following components in sequence: a first lens having negative optical power; a second lens with a concave-convex shape having positive optical power; an aperture stop; a third lens having positive optical power; and a combined lens having a positive combined optical power formed by joining a fourth lens having positive optical power and a fifth lens having negative optical power, wherein the imaging lens satisfies the following formula: 0.825≤D23 / f≤1.850(1-1) 0.48≤L_D3 / f≤1.20 (1-2) in, D23: The interplane distance on the axis between the second lens and the third lens. f: Focal length of the imaging lens L_D3: The center thickness of the third lens.

2. The imaging lens as described in claim 1, satisfying the following formula: -0.120≤f_L1 / f_L45≤-0.010(2) in, f_L1: Focal length of the first lens f_L45: The focal length of the bonding lens.

3. The imaging lens as described in claim 1, satisfying the following formula: 0.180≤f_L3 / f_L2≤0.600 (3) in, f_L2: Focal length of the second lens f_L3: The focal length of the third lens.

4. The imaging lens as described in claim 1, satisfying the following formula: 4.00≤f_L2 / f≤10.00 (4) in, f_L2: The focal length of the second lens.

5. The imaging lens as described in claim 1, satisfying the following formula: -1.00≤f_L1 / f_L3≤-0.30(5) in, f_L1: Focal length of the first lens f_L3: The focal length of the third lens.

6. The imaging lens as described in claim 1, satisfying the following formula: 0.010≤f_L3 / f_L45≤0.150 (6) in, f_L3: The focal length of the third lens f_L45: The focal length of the bonding lens.

7. The imaging lens as described in claim 1, satisfying the following formula: -3.00<G45L1SF<-1.20(7) in, G45L1SF: Described by the following formula G45L1SF=(G4L1Lr+G5L1Rr) / (G4L1Lr-G5L1Rr)(7-1) in, G4L1Lr: Radius of curvature of the object-side lens surface of the fourth lens. G5L1Rr: The radius of curvature of the lens surface on the image plane side of the fifth lens.

8. The imaging lens as described in claim 1, satisfying the following formula: -3.00≤f_L1 / f≤-1.00 (8) in, f_L1: The focal length of the first lens.

9. The imaging lens as described in claim 1, satisfying the following formula: -0.400≤f_L1 / f_L2≤-0.200 (9) in, f_L1: Focal length of the first lens f_L2: The focal length of the second lens.

10. The imaging lens as described in claim 1, The first lens is a concave-convex lens, and The imaging lens satisfies the following formula: 1.00 < G1L1SF < 3.00 (10) in G1L1SF: Expressed by the following formula G1L1SF=(G1L1Lr+G1L1Rr) / (G1L1Lr-G1L1Rr)(10-1) in, G1L1Lr: Radius of curvature of the lens surface on the object side of the first lens. G1L1Rr: The radius of curvature of the lens surface on the image plane side of the first lens.

11. A camera device comprising an imaging lens as claimed in any one of claims 1 to 10, and an imaging element that converts an optical image formed by the imaging lens into an electrical signal on the image plane side of the imaging lens.

Images