Two-piece optical athermalization lens and imaging device

Abstract

The utility model discloses a two-piece optical athermalization lens which comprises a first lens and a second lens which are sequentially arranged from the object side to the image side along the optical axis, the first lens is a meniscus negative lens with the convex face facing the object side, the second lens is a biconvex lens, the focal length of the lens is f, the focal length of the first lens is f1, and the focal length of the second lens is f2, the curvature radius of the intersection point of the object side surface of the first lens and the optical axis is R1, the curvature radius of the intersection point of the image side surface of the first lens and the optical axis is R2, the curvature radius of the intersection point of the object side surface of the second lens and the optical axis is R3, and f, f1, f2, R1, R2 and R3 meet the following relations:-5.6 < f1 / f <-4, 0.6 < f2 / f < 1.2, 1.3 < R1 / R2 < 2.5, and 4.4 < R3 / R1 < 5.4. The athermalization lens can realize the characteristic of temperature self-adaptive optical athermalization, is simple in structure, small in size and light in weight, and can meet the use requirements of a miniaturized uncooled infrared optical system. The utility model further discloses an imaging device.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of optical systems, and particularly relates to a two-piece optical athermalization lens and an imaging device. BACKGROUND

[0002] In the application of infrared optical system imaging, the system is required to maintain good imaging quality within a wide ambient temperature, and mechanical athermalization technology and optical passive athermalization technology can be used to achieve this. The mechanical athermalization technology refers to that when the working environment temperature changes, the mechanical part uses certain elements in the optical system to perform axial displacement, so that the best image plane shift caused by the change of the working environment temperature is compensated. This optical system has problems such as relatively complex structure, large number of lenses, and high cost. Optical passive athermalization is to compensate for the image plane shift caused by the change of the ambient temperature by reasonably combining materials according to the difference between the thermal analysis parameters of the optical materials in the optical system, so as to fix the best image plane and achieve the athermalization design of the system. At present, in order to obtain a wider range of working temperature and clearer imaging quality, a large number of lenses are often used, which leads to an increase in volume and weight and a high cost. CONTENT OF THE UTILITY MODEL

[0003] The technical problem to be solved by the application is that the number of lenses in the existing optical athermalization lens is large, which leads to an increase in the volume and weight of the lens and a high cost. In order to solve this technical problem, a two-piece optical athermalization lens with a small number of lenses and an imaging device are provided.

[0004] The technical scheme provided by the application is as follows:

[0005] A two-piece optical athermalization lens comprises a first lens and a second lens arranged in sequence along an optical axis from an object side to an image side, the first lens is a meniscus negative lens with a convex surface facing the object side, and the second lens is a double convex lens:

[0006] The focal length of the lens is f, the focal length of the first lens is f1, the focal length of the second lens is f2, the curvature radius of the intersection of the object side surface of the first lens and the optical axis is R1, the curvature radius of the intersection of the image side surface of the first lens and the optical axis is R2, and the curvature radius of the intersection of the object side surface of the second lens and the optical axis is R3, wherein f, f1, f2, R1, R2 and R3 satisfy the following relationships:

[0007] -5.6 < f1 / f < -4, 0.6 < f2 / f < 1.2, 1.3 < R1 / R2 < 2.5, and 4.4 < R3 / R1 < 5.4.

[0008] By employing the aforementioned two-element athermalized optical lens, temperature-adaptive athermalized optical characteristics can be achieved. Furthermore, because this lens comprises only two lenses, it has a simple structure, small size, and light weight, meeting the requirements for miniaturized uncooled infrared optical systems. In addition, the reduced number of lenses effectively improves the lens's light transmittance, thereby enhancing the detection and recognition rates of the infrared system.

[0009] Furthermore, an aperture stop is provided between the first lens and the second lens, on the image side of the first lens, or on the object side of the second lens.

[0010] Furthermore, the object-side surface and image-side surface of both the first and second lenses are aspherical, and satisfy the following expression:

[0011]

[0012] Where Z is the distance vector from the vertex of the aspherical surface along the optical axis at a position of height Y, R represents the paraxial radius of curvature of the mirror, k is the conic coefficient, and A, B, C, D, and E are higher-order aspherical coefficients.

[0013] Furthermore, the object-side surface of the second lens has a diffraction structure, which is a ring-shaped structure with the optical axis as the central axis.

[0014] Furthermore, both the first lens and the second lens are chalcogenide glass.

[0015] Furthermore, it also includes a lens barrel, with the first lens and the second lens disposed inside the lens barrel.

[0016] Furthermore, the operating wavelength of the lens is 8~12μm.

[0017] An imaging device includes a two-piece athermalized optical lens as described above and a detector for receiving images from the lens. Attached Figure Description

[0018] The accompanying drawings are provided to further understand this application and form part of the specification. They are used together with the embodiments of this application to explain this application and do not constitute a limitation thereof.

[0019] Figure 1 A schematic diagram of the optical structure of a two-piece athermalized lens provided in an embodiment of this application;

[0020] Figure 2 for Figure 1 A schematic diagram of the field curvature of the shot shown;

[0021] Figure 3 for Figure 1 The diagram shows the distortion of the lens.

[0022] Figure 4 for Figure 1 The MTF chart of the lens shown is displayed at 20°C.

[0023] Figure 5 for Figure 1 The MTF chart of the lens shown is displayed at -40℃.

[0024] Figure 6 for Figure 1 The image shown is the MTF chart of the lens at 80°C.

[0025] Label Explanation:

[0026] 11. First lens; 12. Second lens; 21. Protective window; 22. Detector focal plane array. Detailed Implementation

[0027] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0028] This application provides an imaging device, including a two-piece athermalized optical lens and a detector for receiving the image formed by the lens. Figure 1 As shown, the two-piece athermalized optical lens includes a first lens 11 and a second lens 12 arranged sequentially along the optical axis from the object side to the image side. The detector includes a protective window 21 and a detector focal plane array 22 arranged sequentially. Preferably, the operating wavelength of this lens is 8~12μm.

[0029] In one embodiment, both the first lens 11 and the second lens 12 are chalcogenide glass, exhibiting good transmittance within the 8-12 μm operating wavelength range. Furthermore, the refractive index of chalcogenide glass changes little with temperature, and it is easy to process as it can be polished and turned. This application uses only chalcogenide glass, saving costs. Moreover, chalcogenide glass can be precision molded during mass production, further reducing processing costs.

[0030] In one embodiment, the first lens 11 is a convex-to-object-side crescent negative lens, and the second lens 12 is a biconvex lens, i.e., the first lens 11 has a negative focal power, and the second lens 12 has a positive focal power. It needs to be explained that the focal power represents the refractive power of an optical system to incident parallel light, and the greater the value of the focal power, the more the parallel light beam is folded, and when the focal power is positive, the refraction is convergent, and when the focal power is negative, the refraction is divergent. Further, the object side of the second lens 12 has a central convex structure and an outer peripheral planar structure.

[0031] In one embodiment, an aperture stop is arranged between the first lens 11 and the second lens 12, on the image side of the first lens 11, or on the object side of the second lens 12. Preferably, the aperture stop is arranged between the first lens 11 and the second lens 12 to effectively balance the coma of the lens and reduce the sensitivity while ensuring a larger light flux, and is easier to process.

[0032] In one embodiment, the object side of the second lens 12 has a diffractive structure, which is an annular zone with the optical axis as the central axis. In this way, the diffractive structure can make the object side a diffractive surface, and then the thermal aberration can be corrected through the diffractive surface. Wherein, the above-mentioned diffractive surface satisfies the following phase equation:

[0033]

[0034] Wherein, is the value of the accumulated phase difference of the diffractive surface to the light, M is the diffraction order, N is the serial number of the polynomial coefficient in the series, A i is the 2i power coefficient of p, and p is the normalized radius.

[0035] In one embodiment, the object side and the image side of the first lens 11 and the second lens 12 are aspherical surfaces. The use of aspherical surfaces can correct aberrations such as spherical aberration, coma, astigmatism, etc. Moreover, aspherical surfaces are used instead of spherical surfaces because the ability of spherical surfaces to correct spherical aberration is limited, and if the same effect is to be achieved, the number of lenses and the types of materials must be increased, which will increase the material and weight. Wherein, the above-mentioned aspherical surface satisfies the following expression:

[0036]

[0037] Wherein, Z is the distance from the vertex of the aspherical surface when the aspherical surface is at a height of Y along the optical axis, H is the sag, R represents the paraxial curvature radius of the mirror surface, k is the conic coefficient, and A, B, C, D, and E are high-order aspherical surface coefficients.

[0038] The two-piece optical athermalization lens can realize temperature self-adaptive optical athermalization. Meanwhile, the lens only includes two lenses, and has simple structure, small volume, light weight, and can meet the use requirements of small non-cooled infrared optical systems, and is suitable for performing live recording and security monitoring tasks. In addition, due to the reduction of the number of lenses, the light transmittance of the lens is also effectively improved, and the detection and identification rate of the infrared system is improved.

[0039] In one embodiment, the lens further includes a lens barrel, and the first lens 11 and the second lens 12 are arranged in the lens barrel. By sharing one lens barrel, the coaxial accuracy of the lens is improved.

[0040] In one embodiment, the focal length of the lens is f, the focal length of the first lens 11 is f1, the focal length of the second lens 12 is f2, the radius of curvature of the object side of the first lens 11 at the intersection with the optical axis is R1, the radius of curvature of the image side of the first lens 11 at the intersection with the optical axis is R2, and the radius of curvature of the object side of the second lens 12 at the intersection with the optical axis is R3. Wherein, f, f1, f2, R1, R2, R3 satisfy the following relationships:

[0041] -5.6 < f1 / f < -4, 0.6 < f2 / f < 1.2, 1.3 < R1 / R2 < 2.5, 4.4 < R3 / R1 < 5.4.

[0042] The following describes a specific embodiment of a two-piece optical athermalization lens with a focal length of 19 mm and a full field of view FOV of 30.98°:

[0043] The air gap between the first lens 11 and the second lens 12 is 12.3 mm, the air gap between the second lens 12 and the protective window 21 is 13.84 mm, the center thickness of the first lens 11 is 5.2 mm, the radius of curvature of the object side of the first lens 11 is 13.7 mm, the radius of curvature of the image side is 9.6 mm, the center thickness of the second lens 12 is 4.95 mm, the radius of curvature of the object side of the second lens 12 is 62.6 mm, and the radius of curvature of the image side is -35 mm. The specific parameters are shown in Table 1.

[0044] Table 1

[0045]

[0046] It should be explained that, in combination with Figure 1 , from left to right along the optical axis direction, the left side is the object side, and the right side is the image side. For example, the S1 surface of the first lens 11 is the object side, and the S2 surface is the image side. The other lenses are not described here.

[0047] It should be noted that in the embodiment, the aspheric surface and the diffractive surface satisfy the above expression, and the aspheric surface coefficients are shown in Table 2, and the surface diffractive coefficients are shown in Table 3.

[0048] Table 2

[0049]

[0050] Table 3

[0051]

[0052] It can be understood that the above data is set for the embodiment, and in other embodiments, other data can be used to achieve other effects, which is not limited herein.

[0053] In addition, Figure 2 is a field curvature curve diagram of the embodiment, represented by five wavelengths of 8-12 μm, in units of mm; Figure 3 is a distortion curve diagram of the embodiment, and the distortion curve diagram represents the distortion size value under different field angles, in units of %. Figures 4 to 6 is a modulation transfer function curve diagram of the embodiment at 20°C, -40°C, and 80°C, respectively, representing the comprehensive resolution level of the optical system. Figure 4 From Table 6, it can be seen that the long-wave infrared optical system has corrected various aberrations, and realized athermalization characteristics in a wide temperature range, which is sufficient to meet practical requirements.

[0054] As an example, in the embodiment, f=19 mm, F number=1, focal length f1 of the first lens 11=-104.4 mm, focal length f2 of the second lens 12=14.43 mm, curvature radius R1 of the first lens 11 at the intersection of the object side and the optical axis=13.7 mm, curvature radius R2 of the first lens 11 at the intersection of the image side and the optical column=9.6 mm, and curvature radius R3 of the second lens 12 at the intersection of the object side and the optical axis=62.6 mm.

[0055] It is calculated that f1 / f=-5.49, f2 / f=0.76, R1 / R2=1.43, and R3 / R1=4.57. It can be seen that in the embodiment, the power distribution of the first lens 11 and the second lens 12 satisfies the above requirements, i.e., -5.6

[0056] Although the embodiments of the present application have been shown and described, it can be understood by those of ordinary skill in the art that various changes, modifications, replacements, and variations can be made to the embodiments without departing from the principles and spirits of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A two-element athermalized optical lens, characterized in that, It includes a first lens and a second lens arranged sequentially along the optical axis from the object side to the image side. The first lens is a meniscus negative lens with its convex surface facing the object side, and the second lens is a biconvex lens. The focal length of the lens is f, the focal length of the first lens is f1, the focal length of the second lens is f2, the radius of curvature of the object-side surface of the first lens at the intersection with the optical axis is R1, the radius of curvature of the image-side surface of the first lens at the intersection with the optical axis is R2, and the radius of curvature of the object-side surface of the second lens at the intersection with the optical axis is R3. Wherein, f, f1, f2, R1, R2, and R3 satisfy the following relationship: -5.6<f1 / f<-4, 0.6<f2 / f<1.2, 1.3<R1 / R2<2.5, 4.4<R3 / R1<5.

4.

2. The two-piece athermalized optical lens according to claim 1, characterized in that, An aperture stop is provided between the first lens and the second lens, on the image side of the first lens, or on the object side of the second lens.

3. The two-piece athermalized optical lens according to claim 1, characterized in that, The object-side surface and image-side surface of both the first and second lenses are aspherical and satisfy the following expression: Where Z is the distance vector from the vertex of the aspherical surface along the optical axis at a position of height Y, R represents the paraxial radius of curvature of the mirror, k is the conic coefficient, and A, B, C, D, and E are higher-order aspherical coefficients.

4. The two-piece athermalized optical lens according to claim 1, characterized in that, The object-side surface of the second lens has a diffraction structure, which is a ring-shaped structure with the optical axis as the central axis.

5. The two-piece athermalized optical lens according to claim 1, characterized in that, Both the first lens and the second lens are chalcogenide glass.

6. The two-piece athermalized optical lens according to claim 1, characterized in that, It also includes a lens barrel, with the first lens and the second lens disposed inside the lens barrel.

7. The two-piece athermalized optical lens according to claim 1, characterized in that, The lens operates in the 8~12μm wavelength range.

8. An imaging device, characterized in that, It includes the two-piece athermalized optical lens as described in any one of claims 1-7 and the detector that receives the image from the lens.

Images