A 75mm infrared optical lens

Abstract

This invention discloses a 75mm infrared optical lens, comprising a first lens, a second lens, and a third lens arranged sequentially along the transmission direction of the incident beam; and satisfying the following relationships: 0.2799 / mm < TTL / ImgH / f < 0.3039 / mm, 1.77 < |f12 / f| < 11, and 0.914 < R31 / R32 < 1.172; where TTL is the distance from the object-side surface of the first lens to the image plane of the optical lens on the optical axis, ImgH is the radius of the effective imaging circle of the optical lens, f is the effective focal length of the optical lens, f12 is the combined focal length of the first and second lenses, R31 is the radius of curvature of the object-side surface of the third lens on the optical axis, and R32 is the radius of curvature of the image-side surface of the third lens on the optical axis. This invention's 75mm infrared optical lens, through the selection and design of the lenses, utilizes three lenses to achieve high-quality imaging in a 75mm infrared optical lens, reducing the number of lenses, shrinking the size, and lowering the cost.

Description

Technical Field

[0001] This invention relates to a 75mm infrared optical lens, belonging to the field of infrared optical imaging technology. Background Technology

[0002] Infrared wavelengths range from 0.75µm to 1000µm. Among them, infrared radiation has three bands with high transmittance when passing through the atmosphere: 2-2.6µm, 3-5µm, and 8-14µm, which are three atmospheric windows. Among them, 780nm-1100nm is the near-infrared short wave, 1100nm-2526nm is the near-infrared long wave, collectively referred to as the near-infrared band, 2.5µm-8µm is the mid-infrared, 8µm-15µm is the far-infrared, and 15µm-1000µm is the extreme far-infrared.

[0003] Infrared lenses primarily receive infrared wavelength signals within three windows: 2-2.6µm, 3-5µm, and 8-14µm. Long-wave infrared lenses have a wide range of applications, serving both as specialized infrared lenses and as general-purpose lenses. In other words, depending on the application, infrared lenses can be flexibly used with conventional color cameras, monochrome cameras, and day / night cameras. While monochrome cameras lack infrared cutoff filters, sunlight still contains infrared light, so even in sunlight, their imaging is affected by infrared interference. Therefore, using an infrared lens can effectively improve image quality.

[0004] For high-pixel infrared detectors with long focal lengths, the optical lens size remains relatively large. Furthermore, factors such as the fixed back focal length and mechanical structure design make assembly and adjustment extremely cumbersome and difficult to modify, hindering the miniaturization of the optical lens. Therefore, this invention designs a 75mm infrared optical lens, reducing the number of lenses and lowering the weight and size of the infrared lens while maintaining imaging quality. Summary of the Invention

[0005] This invention provides a 75mm infrared optical lens that can be used with a miniature infrared thermal imaging module with a 1024*768 12um detector. It has fewer lenses, is lightweight, small in size, and has high imaging quality.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0007] A 75mm infrared optical lens includes a first lens, a second lens, and a third lens arranged sequentially along the transmission direction of the incident beam; and satisfies the following relationships: 0.1319 / mm < TTL / ImgH / f < 0.3039 / mm, 1.77 < |f12 / f| < 11, and 0.914 < R31 / R32 < 1.172; where TTL is the distance from the object side of the first lens to the image plane of the optical lens on the optical axis, ImgH is the radius of the effective imaging circle of the optical lens, f is the effective focal length of the optical lens, f12 is the combined focal length of the first and second lenses, R31 is the radius of curvature of the object side of the third lens on the optical axis, and R32 is the radius of curvature of the image side of the third lens on the optical axis.

[0008] The aforementioned lenses require fewer lens elements, reducing space and weight, and improving image quality.

[0009] Along the transmission direction of the incident beam, the two sides of the first lens are the object side and the image side of the first lens, respectively; the two sides of the second lens are the object side and the image side of the second lens, respectively; and the two sides of the third lens are the object side and the image side of the third lens, respectively.

[0010] The first lens is a meniscus lens with positive refractive power, the object side of the first lens is convex, and the image side of the first lens is concave; the second lens is a meniscus lens with positive refractive power, the object side of the second lens is concave, and the image side of the second lens is convex; the third lens is a meniscus lens with positive refractive power, the object side of the third lens is convex, and the image side of the third lens is concave.

[0011] To further improve imaging quality, the aforementioned 75mm infrared optical lens satisfies the following relationship: 0.345 < CT3 / BF < 0.6; where CT3 is the thickness of the third lens on the optical axis, and BF is the minimum distance on the optical axis from the image side of the third lens to the image plane of the optical lens.

[0012] As one preferred implementation, the radius of curvature of the object-side surface of the first lens is 67.067±0.002mm, and the radius of curvature of the image-side surface of the first lens is 102.367±0.002mm; the radius of curvature of the object-side surface of the second lens is -38.849±0.002mm, and the radius of curvature of the image-side surface of the second lens is -37.536±0.002mm; the radius of curvature of the object-side surface of the third lens is 27.687±0.002mm, and the radius of curvature of the image-side surface of the third lens is 30.283±0.002mm.

[0013] To further improve image quality, the image-side surface of the first lens is aspherical; the image-side surface of the second lens is a diffraction surface; and both the object-side and image-side surfaces of the third lens are aspherical. The object-side surfaces of the first and second lenses are both spherical.

[0014] To further improve the stability and imaging effect of the lens, the center thickness of the first lens is 7.60±0.01mm, the center thickness of the second lens is 5.00±0.01mm, and the center thickness of the third lens is 6.00±0.01mm; the center spacing between the first and second lenses is 20.39±0.01mm, and the center spacing between the second and third lenses is 5.08±0.01mm.

[0015] The first lens L1 is made of germanium glass, while the second lens L2 and the third lens L3 are both made of chalcogenide glass. This design not only provides the optical lens with excellent optical performance but also increases its lifespan, vibration and shock resistance, and reduces the impact of temperature on the lenses.

[0016] The above lenses satisfy the following relationship: 1.00 < FNO < 1.01, where FNO is the aperture number of the optical lens.

[0017] The optical lens of this application has an effective focal length f = 75 mm, a field of view (FOV) of 9.4°*7.0°, an optical total length (TTL) of 84.1 mm, and an operating wavelength of 8-14 μm, making it suitable for a 1024*768 12 μm detector.

[0018] The aforementioned lenses can be used in electronic devices such as UAV electronic pods, guidance heads, military products, border and coastal defense equipment, vehicle-mounted turntables, and security monitoring equipment, or in both military and civilian products.

[0019] Any techniques not mentioned in this invention are based on existing technologies.

[0020] The present invention relates to a 75mm infrared optical lens. By selecting and designing the lenses, and utilizing three lenses, high-quality imaging of a 75mm infrared optical lens is achieved, reducing the number of lenses, shrinking the size, and lowering the cost. Attached Figure Description

[0021] Figure 1 This is the optical path diagram of the 75mm infrared optical lens of the present invention;

[0022] Figure 2 This is the MTF diagram of the 75mm infrared optical lens of the present invention;

[0023] Figure 3 This is a dot matrix diagram of the 75mm infrared optical lens of the present invention;

[0024] Figure 4 This is a distortion diagram of the 75mm infrared optical lens of the present invention;

[0025] Figure 5 This is an illumination diagram of the 75mm infrared optical lens of the present invention. Detailed Implementation

[0026] To better understand the present invention, the following embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments. Example

[0027] like Figure 1 As shown, a 75mm infrared optical lens includes a first lens, a second lens, and a third lens arranged sequentially along the transmission direction of the incident light beam, and satisfying the following relationship:

[0028] 0.1319 / mm < TTL / ImgH / f < 0.3039 / mm, 1.77 < |f12 / f| < 11, 0.914 < R31 / R32 < 1.172, 0.345 < CT3 / BF < 0.6; where TTL is the distance on the optical axis from the object side of the first lens to the image plane of the optical lens; ImgH is the radius of the effective imaging circle of the optical lens, which is 7.68mm; f is the effective focal length of the optical lens; f12 is the combined focal length of the first and second lenses, which is 432.75mm; R31 is the radius of curvature of the object side of the third lens on the optical axis; R32 is the radius of curvature of the image side of the third lens on the optical axis; CT3 is the thickness of the third lens on the optical axis; BF is the minimum distance on the optical axis from the image side of the third lens to the image plane of the optical lens, which is 10mm.

[0029] The first lens is a meniscus lens with positive refractive power, the object side of the first lens is convex, and the image side of the first lens is concave; the second lens is a meniscus lens with positive refractive power, the object side of the second lens is concave, and the image side of the second lens is convex; the third lens is a meniscus lens with positive refractive power, the object side of the third lens is convex, and the image side of the third lens is concave.

[0030] The radius of curvature of the object side S1 of the first lens is 67.067 mm, and the radius of curvature of the image side S2 of the first lens is 102.367 mm; the radius of curvature of the object side S3 of the second lens is -38.849 mm, and the radius of curvature of the image side S4 of the second lens is -37.536 mm; the radius of curvature of the object side S5 of the third lens is 27.687 mm, and the radius of curvature of the image side S6 of the third lens is 30.283 mm.

[0031] The center thickness of the first lens is 7.60 mm, the center thickness of the second lens is 5.00 mm, and the center thickness of the third lens is 6.00 mm. The center-to-center distance between the first and second lenses is 20.39 mm, the center-to-center distance between the second and third lenses is 5.08 mm, and the center-to-center distance between the third lens and the image plane is 10 mm. The object-side surfaces of both the first and second lenses are spherical.

[0032] The first lens L1 is made of germanium glass, while the second lens L2 and the third lens L3 are both made of chalcogenide glass IRG206.

[0033] Table 1 shows the parameters of the optical components.

[0034]

[0035] The image-side surface of the first lens, the object-side surface of the third lens, and the image-side surface are all aspherical. The formula for aspherical surfaces is:

[0036]

[0037] The meanings of the quantities in the equation are as follows:

[0038] z is the aspherical lens sagitta along the optical axis; c = 1 / R; R is the radius of curvature of the lens; x is the half-aperture of the lens perpendicular to the optical axis; k is the conic coefficient; a2 a4 a6 a8 a10 a12 a14 are aspherical coefficients, a2 = 0.

[0039] Table 2 Aspherical coefficients of each lens

[0040]

[0041] In the table above, H represents the diameter depth.

[0042] The image-side surface of the second lens is the diffraction surface, and the equation of the diffraction surface is:

[0043]

[0044] The meanings of the quantities in the equation are as follows: c is the lens sagitta along the optical axis of the aspherical surface; c = 1 / R; R is the radius of curvature of the lens; is the half-aperture of the lens perpendicular to the optical axis; k is the quadratic constant; The coefficients are for the first-order diffraction surface.

[0045] Table 3 Diffraction surface coefficients of the image side of the second lens

[0046]

[0047] The parameters of the aforementioned 75mm infrared optical lens are as follows:

[0048] Total optical length TTL = 84.1 mm;

[0049] Focal length: 75mm;

[0050] Aperture FNO: 1.0;

[0051] Detector: 1024*768 12um;

[0052] Operating wavelength: 8-14µm;

[0053] Focusing distance: 7.5m-∞;

[0054] Coating: DLC;

[0055] Average transmission distance: >89%;

[0056] Maximum field of view: 9.4° * 7.0°;

[0057] Application scenarios: guidance heads, military products, electronic pods, border and coastal defense, vehicle-mounted turntables, security monitoring, etc.

[0058] The aforementioned 75mm infrared optical lens helps to shorten the overall length of the optical lens and compress the light path, thereby reducing spherical aberration. It achieves a high imaging quality design while also reducing the size and weight of the optical lens.

[0059] like Figure 2 The lens MTF chart shows that when the imaging radius is below 35, the MTF is a straight line, and the center image is uniform; as shown... Figure 3 The lens dot plot shows that when the image plane is 2mm, the dot distribution is uniform and the lens has a good depth of field. Figure 4 The image shows lens distortion; it can be seen that when the image height is 0.4mm, the distortion is 0.01, indicating slight overall distortion. Figure 5 The image shows the lens illuminance, which is 1, indicating a stable and uniform illuminance.

Claims

1. A 75mm infrared optical lens, characterized in that: The system comprises three lenses: a first lens, a second lens, and a third lens, arranged sequentially along the transmission direction of the incident beam; and satisfying the following relationships: 0.1319 / mm < TTL / ImgH / f < 0.3039 / mm, 1.77 < |f12 / f| < 11, and 0.914 < R31 / R32 < 1.172; where TTL is the distance from the object-side surface of the first lens to the image plane of the optical lens on the optical axis, ImgH is the radius of the effective imaging circle of the optical lens, f is the effective focal length of the optical lens, f12 is the combined focal length of the first and second lenses, R31 is the radius of curvature of the object-side surface of the third lens on the optical axis, and R32 is the radius of curvature of the image-side surface of the third lens on the optical axis. The following relationship must be satisfied: 0.345 < CT3 / BF < 0.6; where CT3 is the thickness of the third lens on the optical axis, and BF is the minimum distance on the optical axis from the image side of the third lens to the image plane of the optical lens. The first lens is a meniscus lens with positive refractive power, the object side of the first lens is convex, and the image side of the first lens is concave; the second lens is a meniscus lens with positive refractive power, the object side of the second lens is concave, and the image side of the second lens is convex; the third lens is a meniscus lens with positive refractive power, the object side of the third lens is convex, and the image side of the third lens is concave.

2. The 75mm infrared optical lens as described in claim 1, characterized in that: The radius of curvature of the object side of the first lens is 67.067±0.002mm, and the radius of curvature of the image side of the first lens is 102.367±0.002mm; the radius of curvature of the object side of the second lens is -38.849±0.002mm, and the radius of curvature of the image side of the second lens is -37.536±0.002mm; the radius of curvature of the object side of the third lens is 27.687±0.002mm, and the radius of curvature of the image side of the third lens is 30.283±0.002mm.

3. The 75mm infrared optical lens as described in claim 1 or 2, characterized in that: The object-side surface of the first lens is spherical, and the image-side surface of the first lens is aspherical; the object-side surface of the second lens is spherical, and the image-side surface of the second lens is a diffraction surface; both the object-side surface and the image-side surface of the third lens are aspherical.

4. The 75mm infrared optical lens as described in claim 1 or 2, characterized in that: The center thickness of the first lens is 7.60±0.01mm, the center thickness of the second lens is 5.00±0.01mm, and the center thickness of the third lens is 6.00±0.01mm; the center spacing between the first and second lenses is 20.39±0.01mm, and the center spacing between the second and third lenses is 5.08±0.01mm.

5. The 75mm infrared optical lens as described in claim 1 or 2, characterized in that: The first lens L1 is made of germanium glass, while the second lens L2 and the third lens L3 are both made of chalcogenide glass.

6. The 75mm infrared optical lens as described in claim 1 or 2, characterized in that: The following relationship must be satisfied: 1.00 < FNO < 1.01, where FNO is the aperture number of the optical lens.

7. The 75mm infrared optical lens as described in claim 1 or 2, characterized in that: The optical lens has an effective focal length f = 75mm, a field of view (FOV) of 9.4°*7.0°, and a total optical length (TTL) of 84.1mm, making it suitable for a 1024*768 12µm detector.

Images