Low-cost lightweight anti-impact long-wave infrared optical system and application lens thereof

Abstract

The embodiment of the application discloses a low-cost lightweight anti-impact long-wave infrared optical system, which comprises, in sequence from an object side to an imaging side along an optical axis, a stop STO, a first lens and a second lens. The object side of the first lens is a convex surface, the image side is a concave surface, and the image side is a diffraction surface. The optical power of the first lens is positive. The object side of the second lens is a convex surface, and the image side is a concave surface. The optical system satisfies 15°mm<(ImgHFOVDT11) / (FnoTTL)<17°mm. On the other hand, the embodiment of the application also provides a long-wave infrared optical lens. The optical system and the lens of the embodiment of the application are mainly composed of two lenses, the number of lenses is small, the structure is simple, and the lens is convenient to process and install. The optical system and the lens have the characteristics of small overall size, low cost, anti-impact and large aperture.

Description

Technical fields: This application relates to an optical system and a lens for its application, particularly a low-cost, large-aperture, lightweight, shock-resistant long-wave infrared optical system and a long-wave infrared optical lens for its application. Background technology: With the maturity and cost reduction of uncooled long-wave infrared detector technology, infrared thermal imaging systems are increasingly used in civilian and military fields such as security monitoring, industrial temperature measurement, and gun aiming. These applications place stringent requirements on infrared optical systems in many aspects: large aperture, low cost, miniaturization, high image quality, and high reliability. However, traditional solutions generally suffer from drawbacks such as a large number of lenses, complex structure, and large size. Summary of the Invention: To overcome the problems of existing infrared optical systems, such as a large number of lenses, complex structure, and large size, this application provides a low-cost, lightweight, shock-resistant long-wave infrared optical system.

[0001] A low-cost, lightweight, shock-resistant long-wave infrared optical system comprises, along the optical axis from the object side to the imaging side, an aperture stop STO, a first lens, and a second lens. The object-side surface of the first lens is convex, the image-side surface is concave, and the image-side surface is a diffraction surface. The optical power of the first lens is positive. The object-side surface of the second lens is convex, and the image-side surface is concave. The optical system satisfies: 15° mm < (ImgH) FOV DT11) / (Fno TTL) <17° mm; Where ImgH is half the diagonal length of the effective imaging area of ​​the infrared detector, FOV is half the maximum field of view of the optical system, DT11 is the maximum effective half-aperture of the first lens object side, Fno is the F number of the optical system, and TTL is the on-axis distance from the first lens object side to the imaging surface.

[0002] On the other hand, this application also provides a long-wave infrared optical lens.

[0003] A long-wave infrared optical lens, wherein the aforementioned low-cost, lightweight, shock-resistant long-wave infrared optical system is installed within the optical lens.

[0004] The optical system and lens of this application embodiment are mainly composed of two lenses in an optimized combination. The number of lenses is small, the structure is simple, and it is easy to process and install. It has the characteristics of small overall size, low cost, impact resistance and large aperture. By combining different lenses and rationally allocating optical power and surface shape, the amount of light entering the optical system can be increased, resulting in higher imaging quality. It is suitable for civilian and military fields such as security monitoring, industrial temperature measurement, and gun aiming. Attached image description: 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.

[0005] Figure 1 This is a schematic diagram of the structure of an embodiment of the optical system or lens of this application; Figure 2 The modulation transfer function curve at room temperature is shown for the optical system or lens embodiment of this application. Figure 3 This is a blur pattern of the optical system or lens embodiment of this application; Figure 4 This is a relative illumination curve for an embodiment of the optical system or lens of this application; Figure 5 This is a schematic diagram of the structure of the optical system or lens according to Embodiment 2 of this application; Figure 6 This is a relative illumination curve for the second embodiment of the optical system or lens of this application; Figure 7 This is a schematic diagram of the structure of the optical system or lens of Embodiment 3 of this application; Figure 8 This is a relative illumination curve for the optical system or lens embodiment three of this application. Detailed implementation method: To make the technical problems, technical solutions, and beneficial effects solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0006] When ordinal numbers such as "first" and "second" are mentioned in the embodiments of this application, unless they actually express the meaning of order according to the context, they should be understood as being used only for distinction.

[0007] This application provides a low-cost, lightweight, shock-resistant long-wave infrared optical system, which includes, along the optical axis from the object side to the imaging side: an aperture stop (STO), a first lens, a second lens, and a protective glass; the object side of the first lens is convex, and the image side is concave, and the image side is a diffraction surface; the optical power of the first lens is positive; the object side of the second lens is convex, and the image side is concave; the optical system satisfies: 15°mm < (ImgH) FOV DT11) / (Fno TTL)<17°mm; where ImgH is half the diagonal length of the effective imaging area of ​​the infrared detector, FOV is half the maximum field of view of the optical system, DT11 is the maximum effective half-aperture of the first lens object side, Fno is the F number of the optical system, and TTL is the on-axis distance from the first lens object side to the imaging surface.

[0008] The optical system of this application embodiment is mainly composed of two optimized lenses. It has a small number of lenses, a simple structure, and is easy to manufacture and install. It features small overall size, low cost, impact resistance, and a large aperture. By combining different lenses and rationally allocating optical power and surface shape, the amount of light entering the optical system can be increased. The parameter optimization of the optical system is used to constrain its overall configuration, balance optical performance and overall optical length, and ensure a relatively balanced aberration and illumination. This ensures excellent imaging quality in a compact structure and is suitable for civilian and military fields such as security monitoring, industrial temperature measurement, and gun aiming.

[0009] The optical system of this application embodiment has an imaging plane resolution of 640. 512, with a pixel size of 12μm.

[0010] Furthermore, as a preferred embodiment of this solution and not a limitation, the optical system satisfies: 45mm <f f1 / TTL < 52mm; where f is the effective optical focal length, f1 is the effective focal length of the first lens, and TTL is the on-axis distance from the object side of the first lens to the imaging plane. This allows for extreme miniaturization of the optical system while ensuring image quality.

[0011] Furthermore, as a preferred embodiment of this solution and not a limitation, the optical system satisfies: 0.4 < (f1 + f2) / f2 < 1.1; where f is the effective focal length, f1 is the effective focal length of the first lens, and f2 is the effective focal length of the second lens. This is used to constrain the optical power distribution between the first lens and the overall optical system, ensuring that each lens is easy to manufacture, fully utilizing the chromatic aberration correction capability of the binary diffraction surface on the first lens, while avoiding the generation of a large number of high-order aberrations and reducing high-order diffraction stray light from the binary diffraction surface.

[0012] Furthermore, as a preferred embodiment of this solution and not a limitation, the optical system satisfies: 16 <DT11 2 / ET1<20; where DT11 is the maximum effective half-aperture of the first lens side surface, and ET1 is the edge thickness of the first lens. This is used to constrain the radial and axial structural ratio of the lens, ensuring that the edge of the first lens has sufficient absolute thickness and bending strength. This effectively resists stress concentration and crack propagation along the lens edge when subjected to high G-value impacts such as gun recoil, preventing edge chipping or shattering. Simultaneously, it avoids excessive mass and inertia caused by excessive edge thickness, preventing increased impact load due to increased weight, thus achieving a synergistic optimization of lightweight design and impact resistance.

[0013] Furthermore, as a preferred embodiment of this solution, and not a limitation, the optical system satisfies: 28 < (R1 + R2) / (DT11 - DT12) < 43; where R1 is the radius of curvature of the object-side surface of the first lens, R2 is the radius of curvature of the image-side surface of the first lens, DT11 is the maximum effective half-aperture of the object-side surface of the first lens, and DT12 is the maximum effective half-aperture of the image-side surface of the first lens. This is used to constrain the variation of the effective aperture on both sides of the first lens, ensuring a uniform thickness distribution at the edge of the first lens; avoiding excessive differences in aperture on both sides, making edge adjustment difficult; and avoiding the apertures of the object-side and image-side surfaces of the first lens being too close, ensuring the aberration adjustment capability of the optical system.

[0014] Furthermore, as a preferred embodiment of this solution and not a limitation, the optical system satisfies: 4 <EPD (f1-R1) / (ImgH DT11)<7; where EPD is the entrance pupil diameter of the optical system, ImgH is half the diagonal length of the effective imaging area of ​​the infrared detector, f1 is the effective focal length of the first lens, R1 is the radius of curvature of the object-side surface of the first lens, and DT11 is the maximum effective half-aperture of the object-side surface of the first lens. This ensures that the angle of the beam incident on the binary diffraction surface is within a reasonable working range, balancing lens manufacturing feasibility and light transmission integrity.

[0015] Furthermore, as a preferred embodiment of this solution and not a limitation, the optical system satisfies: 10 < |(DT21+DT22) / (DT21-DT22)| < 15; where DT21 is the maximum effective half-aperture of the object side of the second lens, and DT22 is the maximum effective half-aperture of the image side of the second lens. This is used to constrain the aperture symmetry of the second lens, avoiding excessively large incident and refraction angles of the beam, which could easily introduce large coma and astigmatism; at the same time, it avoids insufficient optical power of the second lens, ensuring that it can achieve beam convergence and aberration correction.

[0016] Further, as a preferred but non-limiting embodiment of the present solution, the optical system satisfies: 4.0<f×n1 / (Fno×R1)<4.5; where f is the optical effective focal length, n1 is the refractive index of the first lens, Fno is the F-number of the optical system, and R1 is the radius of curvature of the object-side surface of the first lens. Reasonable configuration of each optical parameter of the optical system helps to control the bending degree of the first lens, thereby reducing the processing difficulty of the first lens.

[0017] Still further, as a preferred but non-limiting embodiment of the present solution, the optical system satisfies: 1.0<(SAG1+SAG3) / (SAG1-SAG3)<1.3; where SAG1 is the distance in the direction parallel to the optical axis from the maximum effective clear aperture of the object-side surface of the first lens to the intersection point of the object-side surface of the first lens and the optical axis, and SAG3 is the distance in the direction parallel to the optical axis from the maximum effective clear aperture of the object-side surface of the second lens to the intersection point of the object-side surface of the second lens and the optical axis. This can ensure reasonable distribution of the optical power of the optical system and guarantee the uniformity of image quality.

[0018] Even further, as a preferred but non-limiting embodiment of the present solution, the optical system satisfies: 1.0 ≤ R3 / R4<3.5, where R3 is the radius of curvature of the object-side surface of the first lens, and R4 is the radius of curvature of the image-side surface of the first lens. This is used to define the curvature ratio of the two optical surfaces of the second lens, control the bending shape of the second lens, so that it can fully perform the function of residual aberration compensation.

[0019] Embodiment 1: Specifically, in combination with Figure 1 , in this embodiment, the present optical system sequentially includes, from the object side to the imaging side along the optical axis: a stop STO, a first lens 1, a second lens 2, and a protective glass 3, wherein the stop STO is coplanar with the object-side surface S1 of the first lens 1. The first lens 1 has positive optical power, with its object-side surface S1 being a convex surface and its image-side surface S2 being a concave surface. The second lens 2 has optical power, with its object-side surface S3 being a convex surface and its image-side surface S4 being a concave surface. The protective glass 3 is infrared glass, having an object-side surface S5 and an image-side surface S6. Light from the object side sequentially passes through the respective surfaces S1 to S6 and finally forms an image on the imaging surface S7.

[0020] The basic parameters of the optical system in this embodiment are shown in the following table:

[0021] More specifically, the object-side surface of the first lens 1, and the object-side surface and the image-side surface of the second lens 2 are all aspheric surfaces, and their even-order aspheric surface profiles satisfy the following equation:

[0022] Where z is the distance from the vertex of the even-order aspherical surface along the optical axis, r is the height from the optical axis, c is the curvature 1 / R, and R is the radius of curvature at the vertex of the lens; k is the conic coefficient, and a2, a3, a4, a5, a6, a7, and a8 are the higher-order coefficients of the aspherical surface. For example, the following table details the conic coefficient k and the higher-order coefficients a2, a3, a4, a5, a6, a7, and a8 of the aspherical lens surface in this embodiment, using a feasible implementation method:

[0023] More specifically, the image-side surface S2 of the first lens 1 is a binary diffraction surface, and the phase distribution of the diffraction surface satisfies the following expression: Where Φ is the binary diffraction phase, M is the diffraction order, A1 and A2 are the binary diffraction phase coefficients, and ρ is the normalized radius. The table below shows the binary diffraction phase coefficients and normalized radii that can be used in this embodiment.

[0024]

[0025] Figure 2 The figure shows the modulation transfer function curve of the optical system of this embodiment at room temperature. Figure 3 The diffusion pattern of the optical system in this embodiment is shown. Figure 4 The relative illumination curve of the optical system in this embodiment is shown. From... Figure 2 As can be seen, the optical system in this embodiment can achieve good imaging quality.

[0026] Example 2: Specifically, in combination with Figure 5 In this embodiment, the optical system comprises, along the optical axis from the object side to the imaging side, an aperture stop STO, a first lens 1, a second lens 2, and a protective glass 3, wherein the aperture stop STO and the object-side surface S1 of the first lens 1 are coplanar. The first lens 1 has positive optical power, its object-side surface S1 is convex, and its image-side surface S2 is concave. The second lens 2 has optical power, its object-side surface S3 is convex, and its image-side surface S4 is concave. The protective glass 3 is infrared glass, having an object-side surface S5 and an image-side surface S6. Light from the object side passes sequentially through each surface S1 to S6 and is finally imaged onto the imaging surface S7.

[0027] The basic parameters of the optical system in this embodiment are shown in the table below:

[0028] More specifically, the object-side surface of the first lens 1 and the object-side surface and image-side surface of the second lens 2 are both aspherical surfaces, and their even-order aspherical surface shapes satisfy the following equation:

[0029] Where z is the distance from the vertex of the even-order aspherical surface along the optical axis, r is the height from the optical axis, c is the curvature 1 / R, and R is the radius of curvature at the vertex of the lens; k is the conic coefficient, and a2, a3, a4, a5, a6, a7, and a8 are the higher-order coefficients of the aspherical surface. For example, the following table details the conic coefficient k and the higher-order coefficients a2, a3, a4, a5, a6, a7, and a8 of the aspherical lens surface in this embodiment, using a feasible implementation method:

[0030] More specifically, the image-side surface S2 of the first lens 1 is a binary diffraction surface, and the phase distribution of the diffraction surface satisfies the following expression: Where Φ is the binary diffraction phase, M is the diffraction order, A1 and A2 are the binary diffraction phase coefficients, and ρ is the normalized radius. The table below shows the binary diffraction phase coefficients and normalized radii that can be used in this embodiment.

[0031]

[0032] Figure 6 The relative illumination curve of the optical system in this embodiment is shown. Figure 6 As can be seen, the optical system in this embodiment can achieve good imaging quality.

[0033] Example 3: Specifically, in combination with Figure 7 In this embodiment, the optical system comprises, along the optical axis from the object side to the imaging side, an aperture stop STO, a first lens 1, a second lens 2, and a protective glass 3, wherein the aperture stop STO and the object-side surface S1 of the first lens 1 are coplanar. The first lens 1 has positive optical power, its object-side surface S1 is convex, and its image-side surface S2 is concave. The second lens 2 has optical power, its object-side surface S3 is convex, and its image-side surface S4 is concave. The protective glass 3 is infrared glass, having an object-side surface S5 and an image-side surface S6. Light from the object side passes sequentially through each surface S1 to S6 and is finally imaged onto the imaging surface S7.

[0034] The basic parameters of the optical system in this embodiment are shown in the table below:

[0035] More specifically, the object-side surface of the first lens 1 and the object-side surface and image-side surface of the second lens 2 are both aspherical surfaces, and their even-order aspherical surface shapes satisfy the following equation:

[0036] Where z is the distance from the vertex of the even-order aspherical surface along the optical axis, r is the height from the optical axis, c is the curvature 1 / R, and R is the radius of curvature at the vertex of the lens; k is the conic coefficient, and a2, a3, a4, a5, a6, a7, and a8 are the higher-order coefficients of the aspherical surface. For example, the following table details the conic coefficient k and the higher-order coefficients a2, a3, a4, a5, a6, a7, and a8 of the aspherical lens surface in this embodiment, using a feasible implementation method:

[0037] More specifically, the image-side surface S2 of the first lens 1 is a binary diffraction surface, and the phase distribution of the diffraction surface satisfies the following expression: Where Φ is the binary diffraction phase, M is the diffraction order, A1 and A2 are the binary diffraction phase coefficients, and ρ is the normalized radius. The table below shows the binary diffraction phase coefficients and normalized radii that can be used in this embodiment.

[0038]

[0039] Figure 8 The relative illumination curve of the optical system in this embodiment is shown. From... Figure 8 As can be seen, the optical system in this embodiment can achieve good imaging quality.

[0040] The basic data of each optical system in the above embodiments one to three are as follows:

[0041] In the above embodiments one to three, the conditional expressions of each optical system in the corresponding embodiments satisfy the conditions in the table below:

[0042] A long-wave infrared optical lens, wherein the aforementioned low-cost, lightweight, shock-resistant long-wave infrared optical system is installed within the optical lens.

[0043] The lens in this embodiment is mainly composed of two optimized lenses. It has a small number of lenses, a simple structure, and is easy to manufacture and install. It features small overall size, low cost, impact resistance, and a large aperture. By combining different lenses and rationally allocating optical power and surface shape, the amount of light entering the optical system can be increased. The parameters of the optical system are optimized to constrain its overall configuration, balance optical performance and overall optical length, and ensure relatively balanced aberration and illumination. This ensures excellent imaging quality in a compact structure, making it suitable for civilian and military fields such as security monitoring, industrial temperature measurement, and gun aiming.

[0044] The above description provides one or more embodiments in conjunction with specific content, and does not imply that the specific implementation of this application is limited to these descriptions. Any methods or structures that are similar to or identical 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 low-cost, lightweight, shock-resistant long-wave infrared optical system, comprising, from the object side to the imaging side along the optical axis: a stop STO, a first lens, and a second lens; characterized in that the object side of the first lens is a convex surface, the image side thereof is a concave surface, the image side is a diffractive surface, and the first lens has a positive optical power; the object side of the second lens is a convex surface, and the image side thereof is a concave surface; The optical system satisfies: 15° mm < (ImgH) FOV DT11) / (Fno TTL) <17° mm; wherein ImgH is half the diagonal length of the effective imaging area of the infrared detector, FOV is half the maximum field angle of the optical system, DT11 is the maximum effective clear half-aperture of the object side of the first lens, Fno is the F-number of the optical system, and TTL is the on-axis distance from the object side of the first lens to the image plane.

2. The low-cost, lightweight, shock-resistant long-wave infrared optical system as described in claim 1, characterized in that, The optical system meets the following requirements: 45mm <f f1 / TTL<52mm; where f is the effective optical focal length, f1 is the effective focal length of the first lens, and TTL is the on-axis distance from the object side of the first lens to the imaging plane.

3. The low-cost, lightweight, shock-resistant long-wave infrared optical system as described in claim 1 or 2, characterized in that, The optical system satisfies: 0.4<(f1+f2) / f2<1.1; wherein f is the effective focal length of the optical system, f1 is the effective focal length of the first lens, and f2 is the effective focal length of the second lens.

4. The low-cost, lightweight, shock-resistant long-wave infrared optical system as described in claim 1 or 2, characterized in that, The optical system meets the following requirements: 16 <DT11 2 / ET1<20; where DT11 is the maximum effective half-aperture of the object side of the first lens, and ET1 is the edge thickness of the first lens.

5. The low-cost, lightweight, shock-resistant long-wave infrared optical system as described in claim 1 or 2, characterized in that, The optical system satisfies: 28<(R1+R2) / (DT11-DT12)<43; wherein R1 is the radius of curvature of the object side of the first lens, R2 is the radius of curvature of the image side of the first lens, DT11 is the maximum effective clear half-aperture of the object side of the first lens, and DT12 is the maximum effective clear half-aperture of the image side of the first lens.

6. The low-cost, lightweight, shock-resistant long-wave infrared optical system as described in claim 1 or 2, characterized in that, The optical system meets the following requirements: 4 <EPD (f1-R1) / (ImgH DT11)<7; where EPD is the entrance pupil diameter of the optical system, ImgH is half the diagonal length of the effective imaging area of ​​the infrared detector, f1 is the effective focal length of the first lens, R1 is the radius of curvature of the object-side surface of the first lens, and DT11 is the maximum effective half-aperture of the object-side surface of the first lens.

7. The low-cost, lightweight, shock-resistant long-wave infrared optical system as described in claim 1 or 2, characterized in that, The optical system satisfies: 10<|(DT21+DT22) / (DT21-DT22)|<15; wherein DT21 is the maximum effective clear half-aperture of the object side of the second lens, and DT22 is the maximum effective clear half-aperture of the image side of the second lens.

8. The low-cost, lightweight, shock-resistant long-wave infrared optical system as described in claim 1 or 2, characterized in that, The optical system satisfies: 4.0<f×n1 / (Fno×R1)<4.5; wherein f is the effective focal length of the optical system, n1 is the refractive index of the first lens, Fno is the F-number of the optical system, and R1 is the radius of curvature of the object side of the first lens.

9. The low-cost, lightweight, impact-resistant long-wave infrared optical system according to claim 1 or 2, characterized in that: The optical system satisfies: 1.0<(SAG1+SAG3) / (SAG1-SAG3)<1.3; wherein SAG1 is the distance in the direction parallel to the optical axis from the maximum effective clear aperture of the object side of the first lens to the intersection point of the object side of the first lens and the optical axis, and SAG3 is the distance in the direction parallel to the optical axis from the maximum effective clear aperture of the object side of the second lens to the intersection point of the object side of the second lens and the optical axis; and / or The optical system satisfies: 1.0 ≤ R3 / R4<3.5, wherein R3 is the radius of curvature of the object side of the first lens, and R4 is the radius of curvature of the image side of the first lens.

10. A long-wave infrared optical lens, characterized in that, An optical lens is internally equipped with the low-cost, lightweight, impact-resistant long-wave infrared optical system according to any one of claims 1 to 9.

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