Large-field-angle medium-wave infrared camera lens

Abstract

The utility model relates to a large-field-angle medium-wave infrared pick-up lens, belongs to the technical field of optical imaging, and solves the problem that the compatibility of a large field angle and high picture quality cannot be satisfied in the prior art. The medium-wave infrared pick-up lens sequentially comprises a first lens with negative focal power, a second lens with negative focal power, a third lens with positive focal power, a fourth lens with negative focal power, a fifth lens with positive focal power and a sixth lens with negative focal power from outside to inside along an optical axis, the seventh lens has positive focal power; and the eighth lens has positive focal power. At least five mirror surfaces in the eight lenses are aspheric surfaces; the effective focal length of the pick-up lens, the effective focal length of the second lens, the effective focal length of the fifth lens and the effective focal length of the eighth lens meet the following formula: # imgabs0 #. The large-field-angle medium-wave infrared pick-up lens provided by the utility model has a large field angle and also has a high-definition display picture.

Description

Technical Field

[0001] The utility model relates to the technical field of optical imaging, in particular to a medium-wave infrared camera lens with a large viewing angle. Background Art

[0002] Medium-wave infrared optical imaging is widely used in various fields such as military and civilian. With the continuous update of market demand, higher requirements are also put forward for infrared optical imaging technology.

[0003] Medium-wave infrared optical imaging has seen a breakdown of various performance indicators at different application levels. Field of view is a key indicator of medium-wave infrared camera lenses. Better balancing large field of view and high image quality is one of the important goals for improving the application of medium-wave infrared camera lenses.

[0004] Currently, most of the medium-wave infrared camera lenses on the market have a small field of view. Even if they can achieve a larger field of view, the image quality is reduced, and the requirements of compatibility between a large field of view and high-definition image quality cannot be met. Utility Model Content

[0005] In view of the above analysis, the utility model aims to provide a medium-wave infrared camera lens with a large field of view, so as to solve the problem of balancing the large field of view and high-definition image quality in the prior art.

[0006] The purpose of this utility model is mainly achieved through the following technical solutions:

[0007] A medium-wave infrared camera lens with a large field of view, the camera lens comprises, from the outside to the inside along the optical axis: a first lens with negative focal power, whose outer side surface is convex; a second lens with negative focal power, whose outer side surface is concave; a third lens with positive focal power, whose inner side surface is convex; a fourth lens with negative focal power, whose outer side surface is concave; a fifth lens with positive focal power, whose outer side surface is convex and whose inner side surface is concave; a sixth lens with negative focal power, whose inner side surface is concave; a seventh lens with positive focal power, whose outer side surface is concave; and an eighth lens with positive focal power, whose outer side surface is convex; at least five mirror surfaces of the eight lenses are aspherical; the effective focal length f of the camera lens, the effective focal length F2 of the second lens, the effective focal length F5 of the fifth lens and the effective focal length F8 of the eighth lens satisfy the following:

[0008]

[0009] Furthermore, the effective focal length f of the camera lens, the effective focal length F5 of the fifth lens, and the effective focal length F6 of the sixth lens satisfy:

[0010] Furthermore, the radius of curvature R of the inner side surface of the first lens of the camera lens isS2 , the radius of curvature R of the outer side surface of the seventh lens S13 The effective focal length F1 of the first lens and the effective focal length F7 of the seventh lens satisfy:

[0011] Furthermore, the infrared refractive index IN2 of the second lens at 4300nm, the infrared refractive index IN5 of the fifth lens at 4300nm, the center thickness TL2 of the second lens, and the center thickness TL5 of the fifth lens of the camera lens satisfy:

[0012] Furthermore, the infrared refractive index IN3 of the third lens at 4300nm, the infrared refractive index IN8 of the eighth lens at 4300nm, the center thickness TL3 of the third lens, and the center thickness TL8 of the eighth lens of the camera lens satisfy:

[0013] Furthermore, the edge thickness TE5 of the fifth lens and the center thickness TL5 of the fifth lens of the camera lens satisfy:

[0014] Furthermore, the effective focal length F2 of the second lens, the effective focal length F3 of the third lens, the effective focal length F5 of the fifth lens, the effective focal length F6 of the sixth lens, the distance TA1 from the inner side surface of the first lens to the outer side surface of the second lens, and the distance TA6 from the inner side surface of the sixth lens to the outer side surface of the seventh lens of the camera lens satisfy:

[0015] Furthermore, the camera lens also includes an infrared window, an infrared filter, an aperture and a photosensitive chip which are sequentially arranged inside the eighth lens; the effective semi-aperture D of the eighth lens surface is S16 , the distance BFL from the outside of the infrared window to the photosensitive chip satisfies: The light from the external environment passes through eight lenses, infrared windows, infrared filters, apertures and photosensitive chips in sequence, and is finally imaged on the photosensitive chip.

[0016] Furthermore, the effective semi-aperture D of the outer side surface of the first lens of the camera lens S1 The distance TTL from the outer side of the first lens to the photosensitive chip on the optical axis meets the following conditions:

[0017]

[0018] Furthermore, the effective focal length f, half field angle semiFOV, and photosensitive chip height semiIMH of the camera lens satisfy:

[0019] Compared with the prior art, the utility model has the following beneficial effects:

[0020] 1. The utility model reasonably distributes the optical power of eight lenses with optical power, combines the limitation of the effective focal length of the second lens, the effective focal length of the fifth lens and the effective focal length of the eighth lens and uses an aspherical surface to achieve compatibility of the medium-wave infrared camera lens with a large field of view and high-definition picture quality.

[0021] 2. By reasonably adjusting parameters such as curvature, semi-aperture, and distance, the spherical aberration and chromatic aberration, field curvature, and astigmatism in the camera lens aberrations are improved, so that the camera lens has better aberration correction and the display image clarity is optimized.

[0022] In the present invention, the above-mentioned technical solutions can also be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the following content, and some advantages can be obvious from the description or understood by implementing the present invention. The purpose and other advantages of the present invention can be achieved and obtained through the contents specifically pointed out in the text and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings are only used for the purpose of illustrating specific embodiments and are not to be considered as limiting the present invention. In the entire drawings, the same reference symbols represent the same components.

[0024] Figure 1 A schematic diagram of an optical system according to an embodiment of the present application;

[0025] Figure 2 A schematic diagram of field curvature distortion according to an embodiment of the present application;

[0026] Figure 3 A schematic diagram of vertical axis chromatic aberration according to an embodiment of the present application;

[0027] Figure 4 This is a schematic diagram of the MTF curve of an embodiment of the present application;

[0028] Figure 5 It is a schematic diagram of the relative illumination of the embodiment of the present application.

[0029] Reference numerals:

[0030] L1-first lens; L2-second lens; L3-third lens; L4-fourth lens; L5-fifth lens; L6-sixth lens; L7-seventh lens; L8-eighth lens; L9-infrared window; L10-infrared filter; SS-aperture surface; SENSOR-photosensitive chip; S1-outer side of the first lens; S2-inner side of the first lens; S3-outer side of the second lens; S4-inner side of the second lens; S5-outer side of the third lens; S6-inner side of the third lens; S7- The outer side surface of the four lenses; S8-the inner side surface of the fourth lens; S9-the outer side surface of the fifth lens; S10-the inner side surface of the fifth lens; S11-the outer side surface of the sixth lens; S12-the inner side surface of the sixth lens; S13-the outer side surface of the seventh lens; S14-the inner side surface of the seventh lens; S15-the outer side surface of the eighth lens; S16-the inner side surface of the eighth lens; S17-the outer side surface of the infrared window; S18-the inner side surface of the infrared window; S19-the outer side surface of the infrared filter; S20-the inner side surface of the infrared filter; DETAILED DESCRIPTION

[0031] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of the present application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0032] A specific embodiment of the utility model discloses a medium-wave infrared camera lens with a large field of view, such as Figure 1 shown.

[0033] The camera lens includes, from the outside to the inside along the optical axis: a first lens with negative focal power, whose outer side surface is convex; a second lens with negative focal power, whose outer side surface is concave; a third lens with positive focal power, whose inner side surface is convex; a fourth lens with negative focal power, whose outer side surface is concave; a fifth lens with positive focal power, whose outer side surface is convex and whose inner side surface is concave; a sixth lens with negative focal power, whose inner side surface is concave; a seventh lens with positive focal power, whose outer side surface is concave; and an eighth lens with positive focal power, whose outer side surface is convex; at least five of the eight lenses are aspherical. The outer side is the side of the camera lens close to the external environment, and the inner side is the side of the camera lens close to the photosensitive chip.

[0034] The effective focal length f of the camera lens, the effective focal length F2 of the second lens, the effective focal length F5 of the fifth lens and the effective focal length F8 of the eighth lens meet the following conditions:

[0035]

[0036] Meeting the above-mentioned focal length conditions can control the proportion of the optical power of the second lens, the fifth lens, and the eighth lens in the lens, balance the refractive power of the front and rear lens groups, and achieve a wide field of view while improving the clarity of the display image by reasonably allocating optical power and using aspherical surface shapes.

[0037] Preferred:

[0038]

[0039] Based on the further improvement of the above solution, the effective focal length f of the camera lens, the effective focal length F5 of the fifth lens and the effective focal length F6 of the sixth lens meet the following conditions:

[0040]

[0041] When the above conditions are met, the refractive power of the sixth lens is increased, while the sensitivity of the fifth lens is reduced.

[0042]

[0043] Furthermore, the radius of curvature R of the inner side surface of the first lens of the camera lens is S2 , the radius of curvature R of the outer side surface of the seventh lens S13 The effective focal length F1 of the first lens and the effective focal length F7 of the seventh lens satisfy the following conditions:

[0044]

[0045] When the above conditions are met, the difference in sagittal height between the inner side of the first lens and the outer side of the seventh lens can be controlled while ensuring the optical power of the first lens and the seventh lens, which is beneficial to reducing the incident angle and the exit angle of the light on the two mirror surfaces of the first lens and the seventh lens.

[0046]

[0047] Furthermore, the infrared refractive index IN2 of the second lens at 4300nm, the infrared refractive index IN5 of the fifth lens at 4300nm, the center thickness TL2 of the second lens, and the center thickness TL5 of the fifth lens of the camera lens satisfy the following conditions:

[0048]

[0049] The refractive index of the third lens and the eighth lens of the camera lens and the center thickness of the lens meet the following conditions:

[0050]

[0051] Wherein, IN3 is the infrared refractive index of the third lens at 4300nm, IN8 is the infrared refractive index of the eighth lens at 4300nm, TL3 is the center thickness of the third lens, and TL8 is the center thickness of the eighth lens;

[0052] When the above conditions are met, the refractive indices of the second lens, the fifth lens, the third lens, and the eighth lens can be balanced, which is beneficial to improving the spherical aberration and chromatic aberration of the camera lens.

[0053]

[0054]

[0055] Furthermore, the edge thickness TE5 of the fifth lens of the camera lens satisfies the following conditions:

[0056]

[0057] When the above conditions are met, the thickness ratio of the fifth lens can be guaranteed, and the processing difficulty of the fifth lens can be reduced.

[0058]

[0059] Furthermore, the effective focal length F2 of the second lens, the effective focal length F3 of the third lens, the effective focal length F5 of the fifth lens, the effective focal length F6 of the sixth lens, the distance TA1 from the inner side surface of the first lens to the outer side surface of the second lens, and the distance TA6 from the inner side surface of the sixth lens to the outer side surface of the seventh lens of the camera lens meet the following conditions:

[0060]

[0061] When the above conditions are met, the front group focal length and the rear group focal length can be controlled within a reasonable range. Preferably, the above conditions can further meet:

[0062]

[0063] Furthermore, the camera lens also includes an infrared window, an infrared filter, an aperture and a photosensitive chip which are sequentially arranged inside the eighth lens; the effective semi-aperture D of the eighth lens surface is S16 , the distance BFL from the outside of the infrared window to the photosensitive chip satisfies:

[0064]

[0065] The light from the external environment passes through eight lenses, infrared windows, infrared filters, apertures and photosensitive chips in sequence, and is finally imaged on the photosensitive chip.

[0066] When the above conditions are met, the distance between the outer side of the eighth lens and the photosensitive chip can be increased to ensure that the eighth lens does not interfere with the structural components of the photosensitive chip, while ensuring that the lens has sufficient light aperture. Preferably, the above conditions can further meet:

[0067]

[0068] Furthermore, the effective semi-aperture D of the outer side surface of the first lens of the camera lens S1 The distance TTL from the outer side of the first lens to the photosensitive chip on the optical axis meets the following conditions:

[0069]

[0070] Among them, TTL is the lens length. When the above conditions are met, the lens can be guaranteed to have a moderate total length, which is conducive to controlling the overall volume of the lens module.

[0071] Furthermore, the effective focal length f, the half field angle semiFOV and the half height semiIMH of the photosensitive chip of the camera lens meet the following conditions:

[0072]

[0073] When the above conditions are met, the effective focal length and field angle of the camera lens can be ensured to be within a reasonable range, which is conducive to controlling the field curvature and astigmatism of the camera lens. Preferably, the above conditions can further meet:

[0074]

[0075] Specifically, as shown in Table 1, the optical parameters of the camera lens described in this embodiment include the surface type, curvature radius, thickness, semi-aperture and refractive index of each lens.

[0076] Table 1

[0077]

[0078]

[0079] Among them, S1 and S2 are the outer surface and inner surface of the first lens, S3 and S4 are the outer surface and inner surface of the second lens, S5 and S6 are the outer surface and inner surface of the third lens, S7 and S8 are the outer surface and inner surface of the fourth lens, S9 and S10 are the outer surface and inner surface of the fifth lens, S11 and S12 are the outer surface and inner surface of the sixth lens, S13 and S14 are the outer surface and inner surface of the seventh lens, S15 and S16 are the outer surface and inner surface of the eighth lens, S17 and S18 are the outer surface and inner surface of the infrared window, S19 and S20 are the outer surface and inner surface of the infrared filter, SS is the aperture surface, and SENSOR is the photosensitive chip.

[0080] Furthermore, the aspheric surface shape expression is:

[0081]

[0082] Among them, Z is the distance vector height from the vertex of the aspherical surface when the aspherical surface is at a height of r along the optical axis, r is the distance from a point on the aspherical surface to the optical axis, c is the inverse of the radius of curvature of the aspherical surface, k is the cone coefficient of the aspherical surface, and A4, A6, and A8 are the high-order coefficients of the aspherical surface.

[0083] Specifically, as shown in Table 2, it is a table of parameters of aspheric surface type:

[0084] Table 2

[0085] Face number Cone coefficient The fourth-order coefficient A4 Sixth-order coefficient A6 Eighth-order coefficient A8 S3 2.53 2.48E-04 -2.95E-06 0 S6 -0.09 -7.45E-06 -5.67E-07 0 S9 -0.60 -1.07E-05 1.52E-08 0 S15 0.14 1.17E-06 9.50E-10 0 S16 99.43 1.00E-05 -1.09E-08 0

[0086] In this embodiment, the camera lens composed of the above lenses achieves the following indicators:

[0087] Effective focal length f: -7.57mm;

[0088] SemiFOV: 60.0°

[0089] Numerical aperture F: 2.00;

[0090] The distance from the outer side of the first lens to the photosensitive chip is TTL: 132.02mm.

[0091] like Figure 2 As shown in FIG. 1 , it is a schematic diagram of field curvature distortion of an embodiment of the present application, which shows the image field curvature of different field of view rays on the SENSOR. Figure 3 , which is a schematic diagram of vertical axis chromatic aberration of the camera lens of the embodiment of the present application, represents the deviation of light of different wavelengths after passing through the lens. Figure 2 and Figure 3 As shown in the figure, the medium-wave infrared camera lens with a large field of view of this embodiment has good field curvature and chromatic aberration performance. Figure 4As shown in FIG. 1 , it is a schematic diagram of the MTF curve of the embodiment of the present application, which represents the clarity performance at different sensor positions. Figure 5 , which is a schematic diagram of relative illumination of an embodiment of the present application, represents the brightness normalization at different sensor positions. Figure 4 and Figure 5 As shown, the medium-wave infrared camera lens with a large field of view of this embodiment has good clarity performance and uniform illumination distribution.

[0092] Compared with the prior art, the medium-wave infrared camera lens with a large field of view provided in this embodiment reasonably distributes the optical focal length of the lens and adjusts parameters such as curvature, semi-aperture, and distance, so that the camera lens not only has a larger field of view angle, but also has a display image with correct aberrations and high clarity.

[0093] The above is only a preferred specific implementation of this embodiment, but the protection scope of the present invention is not limited to this. Any changes or substitutions that can be easily thought of by any technician familiar with the technical field within the technical scope disclosed in the present invention should be covered by the protection scope of the present invention.

Claims

1. A medium-wave infrared camera lens with a large field of view, characterized in that: The camera lens includes, from the outside to the inside along the optical axis: A first lens having negative optical power, whose outer side surface is convex; A second lens having negative optical power, whose outer side surface is concave; a third lens having positive power, the inner side of which is convex; a fourth lens element having negative optical power, wherein the outer side surface of the fourth lens element is concave; a fifth lens having positive refractive power, whose outer side surface is convex and whose inner side surface is concave; a sixth lens element having negative optical power, wherein the inner side surface of the sixth lens element is concave; a seventh lens element having positive refractive power, whose outer side surface is concave; and an eighth lens having positive power, whose outer side surface is convex; At least five of the eight lenses have aspherical surfaces; The effective focal length f of the camera lens, the effective focal length F2 of the second lens, the effective focal length F5 of the fifth lens and the effective focal length F8 of the eighth lens satisfy:

2. The medium-wave infrared camera lens with a large field of view according to claim 1, characterized in that: The effective focal length f of the camera lens, the effective focal length F5 of the fifth lens, and the effective focal length F6 of the sixth lens satisfy:

3. The medium-wave infrared camera lens with a large field of view according to claim 1, characterized in that: The radius of curvature R of the inner side surface of the first lens S2 , the curvature radius R of the outer side surface of the seventh lens S13 The effective focal length F1 of the first lens and the effective focal length F7 of the seventh lens satisfy:

4. The medium-wave infrared camera lens with a large field of view according to claim 1, characterized in that: The infrared refractive index IN2 of the second lens at 4300nm, the infrared refractive index IN5 of the fifth lens at 4300nm, the center thickness TL2 of the second lens, and the center thickness TL5 of the fifth lens satisfy:

5. The medium-wave infrared camera lens with a large field of view according to claim 1, characterized in that: The infrared refractive index IN3 of the third lens at 4300nm, the infrared refractive index IN8 of the eighth lens at 4300nm, the center thickness TL3 of the third lens, and the center thickness TL8 of the eighth lens satisfy:

6. The medium-wave infrared camera lens with a large field of view according to claim 1, characterized in that: The edge thickness TE5 of the fifth lens and the center thickness TL5 of the fifth lens satisfy:

7. A medium-wave infrared camera lens with a large field of view according to any one of claims 1 to 6, characterized in that: The effective focal length F2 of the second lens, the effective focal length F3 of the third lens, the effective focal length F5 of the fifth lens, the effective focal length F6 of the sixth lens, the distance TA1 from the inner side of the first lens to the outer side of the second lens, and the distance TA6 from the inner side of the sixth lens to the outer side of the seventh lens satisfy:

8. The medium-wave infrared camera lens with a large field of view according to claim 1, characterized in that: The camera lens also includes an infrared window, an infrared filter, an aperture and a photosensitive chip which are sequentially arranged inside the eighth lens; The effective half-aperture D of the eighth lens surface S16 , the distance BFL from the outer side of the infrared window to the photosensitive chip satisfies: The light from the external environment passes through eight lenses, infrared windows, infrared filters, apertures and photosensitive chips in sequence, and is finally imaged on the photosensitive chip.

9. The medium-wave infrared camera lens with a large field of view according to claim 8, characterized in that: The effective semi-aperture D of the outer surface of the first lens S1 The distance TTL from the outer side of the first lens to the photosensitive chip on the optical axis meets the following conditions:

10. The medium-wave infrared camera lens with a large field of view according to claim 9, characterized in that: The effective focal length f, half field of view angle semiFOV, and photosensitive chip height semiIMH of the camera lens meet the following requirements:

Images