A large-angle infrared confocal optical system and an intelligent monitoring lens module using the same

Abstract

The application belongs to the technical field of optical imaging, and particularly relates to a large-angle infrared confocal optical system and an intelligent monitoring lens module applied in the same. The system is mainly composed of five lenses. The first lens has a convex surface or a plane on the object side and a concave surface on the image side, and has a negative optical power; the second lens has a concave surface on the object side and a convex surface on the image side, and has a positive optical power; the third lens has a convex surface on the object side and a convex surface on the image side, and has a positive optical power; the fourth lens has a concave surface on the object side and a concave surface on the image side, and has a negative optical power; and the fifth lens has a convex surface on the object side and a convex surface on the image side, and has a positive optical power. The first lens, the second lens, the fourth lens and the fifth lens are high-transmittance plastic aspheric lenses. The system has a simple and compact structure. By precisely distributing the optical powers of the lenses and adopting the combination of high-transmittance plastic aspheric lenses and glass spherical lenses, the miniaturization and light weight of the lens are effectively realized, and a large field of view and excellent infrared confocal imaging quality are obtained.

Description

[Technical Field]

[0001] This application belongs to the field of optical imaging technology, specifically relating to a wide-angle infrared confocal optical system and its application in intelligent monitoring lens modules. [Background Technology]

[0002] In recent years, with the rapid development of the smart home and security monitoring markets, users have placed higher demands on the miniaturization, lightweighting, wide-angle capabilities, and high imaging quality of surveillance lenses. Traditional surveillance lenses or optical systems often suffer from drawbacks such as complex structure, large size, narrow field of view, and high cost, making it difficult to meet market demands.

[0003] Especially in applications requiring infrared night vision, ensuring clear imaging of both visible and infrared light across different wavelengths—achieving infrared confocal imaging—while maintaining system compactness and low cost, is a current technical challenge in the industry. Therefore, there is an urgent need for an optical system that can balance wide-angle, miniaturized, lightweight design with excellent infrared confocal performance. [Utility Model Content]

[0004] To address the problems of large size, small field of view, and poor infrared confocal performance in existing surveillance lenses, this application provides a large-angle infrared confocal optical system and an intelligent surveillance lens module for its application.

[0005] This application is achieved through the following technical solution:

[0006] A wide-angle infrared confocal optical system, comprising a first lens, a second lens, a third lens, a fourth lens, and a fifth lens sequentially along the optical axis from the object plane to the image plane, is characterized in that...

[0007] The object side of the first lens is convex or flat, and the image side is concave, and its optical power is negative.

[0008] The object plane side of the second lens is concave, and the image plane side is convex, and its optical power is positive.

[0009] The object plane side of the third lens is convex, the image plane side is convex, and its optical power is positive.

[0010] The object plane side of the fourth lens is concave, the image plane side is concave, and its optical power is negative.

[0011] The fifth lens has a convex object plane and a convex image plane, and its optical power is positive.

[0012] The first lens, the second lens, the fourth lens, and the fifth lens are high-transmittance plastic aspherical lenses.

[0013] Each lens in this optical system satisfies the following condition:

[0014] -6.17mm <f1<-5.05mm;

[0015] 20.39mm <f2<24.92mm;

[0016] 6.82mm <f3<8.33mm;

[0017] -5.63mm <f4<-4.61mm;

[0018] 4.24mm <f5<5.19mm;

[0019] Where f1 is the focal length of the first lens, f2 is the focal length of the second lens, f3 is the focal length of the third lens, f4 is the focal length of the fourth lens, and f5 is the focal length of the fifth lens.

[0020] As described above, in a large-angle infrared confocal optical system, each lens of the optical system satisfies the following condition:

[0021] 1.52 <Nd1<1.55,55.15<Vd1<56.27;

[0022] 1.62 <Nd2<1.66,23.29<Vd2<23.76;

[0023] 1.48 <Nd3<1.51,80.79<Vd3<82.42;

[0024] 1.60 <Nd4<1.63,25.54<Vd4<26.05;

[0025] 1.52 <Nd5<1.55,55.15<Vd5<56.27;

[0026] Wherein, Nd1 is the refractive index of the first lens, and Vd1 is the Abbe number of the first lens; Nd2 is the refractive index of the second lens, and Vd2 is the Abbe number of the second lens; Nd3 is the refractive index of the third lens, and Vd3 is the Abbe number of the third lens; Nd4 is the refractive index of the fourth lens, and Vd4 is the Abbe number of the fourth lens; Nd5 is the refractive index of the fifth lens, and Vd5 is the Abbe number of the fifth lens.

[0027] The above-described wide-angle infrared confocal optical system has a total system length that satisfies the following condition: 15mm ≤ TTL ≤ 25mm.

[0028] In the wide-angle infrared confocal optical system described above, the third lens is a glass spherical lens.

[0029] The above describes a wide-angle infrared confocal optical system with a back focal length > 6.3 mm.

[0030] The above describes a wide-angle infrared confocal optical system with a field of view >130°.

[0031] The above-described wide-angle infrared confocal optical system has an objective lens aperture D that satisfies the following condition: 6mm ≤ D ≤ 12mm.

[0032] In the wide-angle infrared confocal optical system described above, the system aperture is located between the second lens and the third lens.

[0033] A smart surveillance lens module includes at least an optical lens, wherein a wide-angle infrared confocal optical system as described in any of the preceding claims is installed within the optical lens.

[0034] Compared with the prior art, this application has the following advantages:

[0035] This invention provides a wide-angle infrared confocal optical system and its application in intelligent monitoring lens modules, mainly composed of five lenses, with a simple and compact structure. By precisely allocating the optical power of each lens and employing a combination of high-transmittance plastic aspherical and glass spherical lenses, the lens is effectively miniaturized and lightweight. It is compatible with 1 / 2.7” Φ6.6mm, 1 / 2.8” Φ6.6mm, 1 / 2.9” Φ6.2mm CMOS chips and even smaller chips, while achieving a wide field of view and excellent infrared confocal imaging quality, meeting the needs of smart home and indoor monitoring applications. [Attached Image Description]

[0036] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 This is a schematic diagram of the structure of the optical system according to an embodiment of this application;

[0038] Figure 2 This is the optical path diagram of the optical system of this application embodiment at a subject-object distance of 300mm;

[0039] Figure 3 This is an MTF curve of the optical system of this application embodiment at a subject-object distance of 300mm;

[0040] Figure 4 This is a transverse chromatic aberration diagram of the optical system of this application embodiment at a subject-object distance of 300 mm;

[0041] Figure 5This is a graph showing the field curvature and distortion of the optical system in this embodiment at a subject-object distance of 300mm.

[0042] Figure 6 This is an MTF curve of the optical system in the embodiment of this application under infrared confocal conditions;

[0043] Figure 7 This is a transverse chromatic aberration diagram of the optical system under infrared confocal conditions according to an embodiment of this application;

[0044] Figure 8 This is a graph of the optical system under infrared confocal conditions in an embodiment of this application.

Detailed Implementation Methods

[0045] To make the technical problems solved by this application, the technical solutions, and the beneficial effects clearer, this application will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of this application and are not intended to limit this application.

[0046] Please see Figures 1 to 8 This application provides a large-angle infrared confocal optical system, which is composed of a first lens L1, a second lens L2, an aperture stop STO, a third lens L3, a fourth lens L4, and a fifth lens L5 sequentially along the optical axis from the object plane to the image plane. The first lens has a convex or flat object plane side and a concave image plane side, and its optical power is negative. The second lens has a concave object plane side and a convex image plane side, and its optical power is positive. The third lens has a convex object plane side and a convex image plane side, and its optical power is positive. The fourth lens has a concave object plane side and a concave image plane side, and its optical power is negative. The fifth lens has a convex object plane side and a convex image plane side, and its optical power is positive. The first, second, fourth, and fifth lenses are high-transmittance plastic aspherical lenses.

[0047] This invention provides a wide-angle infrared confocal optical system and its application in intelligent monitoring lens modules. The system mainly consists of five lenses: L1, L2, L4, and L5 are aspherical, and L3 is spherical, resulting in a simple and compact structure. By precisely allocating the optical power of each lens and employing a combination of high-transmittance plastic aspherical and glass spherical lenses, the lens achieves miniaturization and weight reduction. It is compatible with 1 / 2.7” Φ6.6mm, 1 / 2.8” Φ6.6mm, and 1 / 2.9” Φ6.2mm CMOS chips, as well as smaller chips, while achieving a wide field of view and excellent infrared confocal imaging quality, meeting the needs of smart home and indoor monitoring applications.

[0048] Furthermore, as a preferred embodiment of this solution and not a limitation, each lens of the optical system satisfies the following condition:

[0049] -6.17 mm < f1 < -5.05 mm;

[0050] 20.39 mm < f2 < 24.92 mm;

[0051] 6.82 mm < f3 < 8.33 mm;

[0052] -5.63 mm < f4 < -4.61 mm;

[0053] 4.24 mm < f5 < 5.19 mm;

[0054] Among them, f1 is the focal length of the first lens, f2 is the focal length of the second lens, f3 is the focal length of the third lens, f4 is the focal length of the fourth lens, and f5 is the focal length of the fifth lens.

[0055] Furthermore, as a preferred implementation manner rather than a limitation of this solution, the refractive index Nd1 and Abbe number Vd1 of the first lens L1 satisfy: 1.52 < Nd1 < 1.55, 55.15 < Vd1 < 56.27; the refractive index Nd2 and Abbe number Vd2 of the second lens L2 satisfy: 1.62 < Nd2 < 1.66, 23.29 < Vd2 < 23.76; the refractive index Nd3 and Abbe number Vd3 of the third lens L3 satisfy: 1.48 < Nd3 < 1.51, 80.79 < Vd3 < 82.42; the refractive index Nd4 and Abbe number Vd4 of the fourth lens L4 satisfy: 1.60 < Nd4 < 1.63, 25.54 < Vd4 < 26.05; the refractive index Nd5 and Abbe number Vd5 of the fifth lens L5 satisfy: 1.52 < Nd5 < 1.55, 55.15 < Vd5 < 56.27; significantly improving the confocal performance and imaging quality in the visible to infrared band. By controlling the refractive index and Abbe number of each lens material within a reasonable range, this design can effectively reduce chromatic aberration and optimize lens aberration, thereby effectively improving the imaging quality of the system. This stepped material combination not only simplifies the structure, reduces weight and cost through aspherical design, but more importantly, synergistically optimizes the optical path consistency of light in each band, enabling visible light (0.449–0.68 μm) and infrared light to be clearly imaged on the same focal plane, completely solving the defocus problem of traditional surveillance lenses during day-night switching, thus achieving all-weather high-resolution surveillance in indoor scenarios such as smart homes.

[0056] Furthermore, as a preferred embodiment of this solution and not a limitation, the total length of the optical system satisfies the following condition: 15mm ≤ TTL ≤ 25mm. This size constraint forces the optical design to complete the ultra-wide-angle 132.8° optical path folding and aspherical aberration correction within a limited space, significantly reducing the space occupied by the module in smart home devices and significantly reducing the amount of lens barrel and lens material used. Combined with the application of high-transmittance plastic lenses, the overall weight is reduced by more than 30%. At the same time, the short optical path design effectively suppresses stray light interference and improves the imaging signal-to-noise ratio, while strict tolerance control ensures optical stability in the infrared confocal band, allowing the edge image quality to remain clear even when switching between day and night without mechanical focusing. Ultimately, under the premise of controllable cost, it provides a solution for consumer-grade security products that combines concealment, portability, and all-weather high-definition monitoring capabilities.

[0057] Furthermore, as a preferred embodiment of this solution and not a limitation thereof, the third lens is a glass spherical lens.

[0058] Furthermore, as a preferred embodiment of this solution and not a limitation, the back focal length of the optical system is >6.3mm. This provides critical redundancy for the infrared filter switching mechanism, sensor packaging space, and heat dissipation structure, thereby completely avoiding the mechanical interference and stray light reflection problems caused by traditional short back focal length designs within the constraint of an ultra-compact system length (22.2mm).

[0059] Furthermore, as a preferred embodiment of this solution and not a limitation, the field of view of this optical system is >130°. By using a high-precision aspherical plastic lens, such as the P1 with a -138.7mm large curvature concave surface and a low-distortion optical path architecture, the light incident angle at the edge of the field of view is compressed to within ±66.4°, allowing a single frame to simultaneously capture the crawling trajectory of a child on the ground and the status of a smoke alarm on the ceiling, increasing the coverage area to 1.8 times that of a typical 110° lens.

[0060] Furthermore, as a preferred embodiment of this solution and not a limitation, the objective lens diameter D of the optical system satisfies the following condition: 6mm ≤ D ≤ 12mm. By controlling the objective lens diameter of the optical imaging lens, it is helpful to improve the lens's ability to receive light source energy, acquire as much object-side information as possible, and thus obtain imaging information with higher brightness and resolution. Details in dark areas such as corners and door gaps are still discernible in backlit scenes.

[0061] Furthermore, as a preferred embodiment of this solution and not a limitation, the system aperture is located between the second lens and the third lens.

[0062] Specifically, this is a preferred embodiment of the invention and not a limitation thereof. Figure 1A schematic diagram of the structure of an optical imaging lens according to an embodiment of this application is shown, with an image circle of 6.7 mm; a working distance from 0.3 M to infinity; a focal length of 3.25 mm; a field of view of 132.8°; an objective lens diameter of 9 mm; a working wavelength of 0.449 μm to 0.68 μm in the visible light band; a total system length of 22.2 mm; and a back focal length greater than 6.3 mm.

[0063] like Figure 1 As shown, the first lens L1 has a flat object plane and a concave image plane, with a negative optical power; the second lens L2 has a concave object plane and a convex image plane, with a positive optical power; the third lens L3 has a convex object plane and a convex image plane, with a positive optical power; the fourth lens L4 has a concave object plane and a concave image plane, with a negative optical power; the fifth lens L5 has a convex object plane and a convex image plane, with a positive optical power; and a filter L6; light from the object passes through each surface sequentially and is finally imaged on the imaging plane.

[0064] Table 1 shows the plane, focal length, refractive index, Abbe number, S1 aperture, S2 aperture, coefficient of thermal expansion, density, and material of each lens in the optical imaging lens of the embodiment. All aperture units are millimeters (mm).

[0065] Table 1: Basic Parameters of the Optical System in the Example

[0066]

[0067] Table 2: Lens R-value parameters of the optical system in the example, in millimeters (mm)

[0068]

[0069] Table 3: Lens core thickness parameters of the optical system in the example, in millimeters (mm)

[0070]

[0071] Table 4: Lens aperture parameters of the optical system in the example, in millimeters (mm)

[0072]

[0073] Table 5: Aspherical higher-order parameter values ​​of the lens surface in the example:

[0074]

[0075]

[0076]

[0077]

[0078]

[0079]

[0080]

[0081]

[0082] Table 6: SAG data of the first aspherical lens R1 on the third surface in the embodiment, in millimeters (mm)

[0083]

[0084] Table 7: SAG data of the first aspherical lens R2 on the fourth surface in the embodiment, in millimeters (mm)

[0085]

[0086] Table 8: SAG data of the second aspherical lens R1 on the fifth surface in the embodiment, in millimeters (mm)

[0087]

[0088] Table 9: SAG data of the second aspherical lens R2 on the sixth surface in the embodiment, in millimeters (mm)

[0089]

[0090] Table 10: SAG data of the 4th lens R1 on the 10th surface in the embodiment, in millimeters (mm)

[0091]

[0092] Table 11: SAG data of the 4th lens R2 on the 11th surface in the embodiment, in millimeters (mm)

[0093]

[0094] Table 12: SAG data of the 5th lens R1 on the 12th surface in the embodiment, in millimeters (mm)

[0095]

[0096] Table 13: SAG data of the 5th lens R2 on the 13th surface in the embodiment, in millimeters (mm)

[0097]

[0098] A smart surveillance lens module, comprising at least an optical lens, characterized in that: the optical lens is equipped with a wide-angle infrared confocal optical system as described in any of the preceding claims.

[0099] The working principle of this embodiment is as follows:

[0100] This invention provides a wide-angle infrared confocal optical system and its application in intelligent monitoring lens modules, mainly composed of five lenses, with a simple and compact structure. By precisely allocating the optical power of each lens and employing a combination of high-transmittance plastic aspherical and glass spherical lenses, the lens is effectively miniaturized and lightweight. It is compatible with 1 / 2.7” Φ6.6mm, 1 / 2.8” Φ6.6mm, 1 / 2.9” Φ6.2mm CMOS chips and even smaller chips, while achieving a wide field of view and excellent infrared confocal imaging quality, meeting the needs of smart home and indoor monitoring applications.

[0101] The above are implementation methods provided in conjunction with specific content, and it is not intended that the specific implementation of this application is limited to these descriptions. Any methods or structures that are similar to those of this application, or any technical deductions or substitutions made based on the concept of this application, should be considered within the scope of protection of this application.

Claims

1. A large-angle infrared confocal optical system, comprising a first lens, a second lens, a third lens, a fourth lens, and a fifth lens sequentially along the optical axis from the object plane to the image plane, characterized in that, The object side of the first lens is convex or flat, and the image side is concave, and its optical power is negative. The object plane side of the second lens is concave, and the image plane side is convex, and its optical power is positive. The object plane side of the third lens is convex, the image plane side is convex, and its optical power is positive. The object plane side of the fourth lens is concave, the image plane side is concave, and its optical power is negative. The fifth lens has a convex object plane and a convex image plane, and its optical power is positive. The first lens, the second lens, the fourth lens, and the fifth lens are high-transmittance plastic aspherical lenses; Each lens in this optical system satisfies the following condition: -6.17mm <f1<-5.05mm; 20.39mm <f2<24.92mm; 6.82mm <f3<8.33mm; -5.63mm <f4<-4.61mm; 4.24mm <f5<5.19mm; Where f1 is the focal length of the first lens, f2 is the focal length of the second lens, f3 is the focal length of the third lens, f4 is the focal length of the fourth lens, and f5 is the focal length of the fifth lens.

2. The large-angle infrared confocal optical system according to claim 1, characterized in that, Each lens in this optical system satisfies the following condition: 1.52 <Nd1<1.55,55.15<Vd1<56.27; 1.62 <Nd2<1.66,23.29<Vd2<23.76; 1.48 <Nd3<1.51,80.79<Vd3<82.42; 1.60 <Nd4<1.63,25.54<Vd4<26.05; 1.52 <Nd5<1.55,55.15<Vd5<56.27; Wherein, Nd1 is the refractive index of the first lens, and Vd1 is the Abbe number of the first lens; Nd2 is the refractive index of the second lens, and Vd2 is the Abbe number of the second lens; Nd3 is the refractive index of the third lens, and Vd3 is the Abbe number of the third lens; Nd4 is the refractive index of the fourth lens, and Vd4 is the Abbe number of the fourth lens; Nd5 is the refractive index of the fifth lens, and Vd5 is the Abbe number of the fifth lens.

3. The large-angle infrared confocal optical system according to claim 1, characterized in that, The total length of the optical system satisfies the following condition: 15mm ≤ TTL ≤ 25mm.

4. The large-angle infrared confocal optical system according to claim 1, characterized in that, The third lens is a glass spherical lens.

5. A large-angle infrared confocal optical system according to claim 1, characterized in that, The back focal length of this optical system is >6.3mm.

6. A large-angle infrared confocal optical system according to claim 1, characterized in that, The field of view of this optical system is >130°.

7. A large-angle infrared confocal optical system according to claim 1, characterized in that, The objective lens diameter D of the optical system satisfies the following condition: 6mm ≤D≤12mm.

8. A large-angle infrared confocal optical system according to claim 1, characterized in that, The system aperture is located between the second lens and the third lens.

9. An intelligent surveillance lens module, comprising at least an optical lens, characterized in that: The optical lens is equipped with a large-angle infrared confocal optical system as described in any one of claims 1-8.

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