Medium-wave continuous zooming refrigeration type infrared lens

Abstract

The invention discloses a medium-wave continuous zooming refrigeration type infrared lens, which is provided with a first lens with positive focal power, a second lens with negative focal power, a third lens with positive focal power and a rear fixing group consisting of a fourth lens, a fifth lens, a sixth lens and a seventh lens in sequence from left to right along the propagation direction of light, an optical filter and a diaphragm are sequentially arranged behind the rear fixing group; the seven lenses comprise a meniscus aspheric lens with the convex surface bent towards the object side, a biconcave aspheric lens, a meniscus aspheric lens with the convex surface bent towards the image side, a meniscus biconvex lens with positive focal power and an aspheric lens with the positive focal power and the convex surface bent towards the image side. The convex surface of the aspherical lens is bent towards the image side; the convex surface of the aspherical lens is bent towards the object side; according to the invention, the capability of identifying and detecting a long-distance target is greatly improved, so that the operating distance of investigation and striking equipment is increased.

Description

Technical Field

[0001] The invention belongs to the field of optical imaging systems, and in particular relates to a 20-fold medium-wave continuous zoom refrigeration type infrared optical lens. Background Art

[0002] In recent years, infrared thermal imaging technology has been widely used in the fields of aviation pods, drone remote sensing, etc. Compared with uncooled medium-wave infrared detectors, the market demand for cooled medium-wave infrared detectors is increasing due to their high sensitivity and long detection distance.

[0003] The cooled medium-wave infrared detector can be matched with a variety of continuous zoom lenses to achieve the purpose of large field of view search at the short focal end and small field of view identification at the long focal end.

[0004] However, the market currently has increasingly higher requirements for the size and weight of medium-wave infrared continuous zoom lenses. Medium-wave infrared continuous zoom lenses with small size and compact structure are the future development trend of cooled medium-wave infrared lenses. Summary of the invention

[0005] In view of the above shortcomings of the prior art, the present invention provides a medium-wave continuous zoom cooled infrared lens with a focal length of 15 to 300 mm, a zoom ratio of 20 times, and an F# of 4. The lens has the characteristics of a large zoom ratio and high resolution, and is suitable for cameras with higher resolutions, as well as for some airborne optoelectronic equipment that has strict requirements on system size and weight.

[0006] The technical solution adopted by the present invention to solve the technical problem is: a medium-wave continuous zoom refrigeration type infrared lens, which is provided with a first lens with positive focal length as a front fixed group, a second lens with negative focal length as a zoom group, a third lens with positive focal length as a compensation group, and a rear fixed group composed of a fourth lens, a fifth lens, a sixth lens, and a seventh lens in sequence from left to right along the propagation direction of light, and a filter and an aperture are arranged in sequence behind the rear fixed group; the first lens is a meniscus aspheric lens with a convex surface bent toward the object side, the second lens is a biconcave aspheric lens, the third lens is a meniscus aspheric lens with a convex surface bent toward the image side, the fourth lens is a meniscus biconvex lens with positive focal length, the fifth lens is an aspheric lens with positive focal length and a convex surface bent toward the image side, the sixth lens is an aspheric lens with positive focal length and a convex surface bent toward the image side, and the seventh lens is an aspheric lens with positive focal length and a convex surface bent toward the object side.

[0007] The medium-wave continuous zoom refrigerated infrared lens has an air spacing of L1±0.01mm between the first lens and the second lens, L1=13.74mm-52.22mm, an air spacing of L2±0.01mm between the second lens and the third lens, L2=120mm-5mm, an air spacing of L3±0.01mm between the third lens and the rear fixed group, L3=23.49mm-100mm, an air spacing of 35.99±0.01mm between the fourth lens and the fifth lens, an air spacing of 8.89±0.01mm between the fifth lens and the sixth lens, and an air spacing of 10±0.01mm between the sixth lens and the seventh lens.

[0008] The medium-wave continuous zoom refrigerated infrared lens has a first lens material of silicon, a second lens material of germanium, a third lens material of silicon, a fourth lens material of silicon, a fifth lens material of germanium, a sixth lens material of silicon, and a seventh lens material of silicon.

[0009] The medium-wave continuous zoom refrigerated infrared lens has a first lens center thickness of 9.95±0.01mm, a second lens center thickness of 9±0.01mm, a third lens center thickness of 5±0.01mm, a fourth lens center thickness of 5.47±0.01mm, a fifth lens center thickness of 3.1±0.01mm, a sixth lens center thickness of 3.41±0.01mm, and a seventh lens center thickness of 3.92±0.01mm.

[0010] The medium-wave continuous zoom refrigerated infrared lens has an optical system with a focal length of 15 to 300 mm and an F number of 4; it is suitable for a CCD or CMOS imaging device with a pixel number of 640×512 and a pixel size of 15μm×15μm.

[0011] The beneficial effects of the present invention are as follows: the present invention adopts aspheric surfaces to reduce various aberrations including chromatic aberration, so that the optical system obtains relatively good imaging quality; the entire optical system plus filters are composed of a total of eight lenses, which is a small number and has the advantages of high resolution, large magnification ratio and small size; the focal length of the optical system is 10 to 300 mm, which greatly improves the recognition and detection capabilities of long-distance targets, thereby increasing the effective distance of reconnaissance and strike equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a schematic diagram of each component of the optical structure of the present invention; Figure 2 The optical system of the present invention in the short-focus state; Figure 3 The optical system of the present invention in the mid-focus state; Figure 4The optical system of the present invention in the telephoto state; Figure 5 It is a transfer function diagram of the optical system in the short-focus state of the present invention at a spatial frequency of 33lp / mm; Figure 6 It is a transfer function diagram of the optical system in the mid-focus state of the present invention at a spatial frequency of 33lp / mm; Figure 7 It is a transfer function diagram of the optical system in the telephoto state of the present invention at a spatial frequency of 33lp / mm; Figure 8 This is a field curvature distortion diagram of the optical system in the short-focus state of the present invention; Fig. 9 is a field curvature distortion diagram of the optical system in the mid-focus state of the present invention; Fig.10 This is a field curvature distortion diagram of the optical system in the telephoto state of the present invention.

[0013] The figures are marked as follows: 1—first lens, 2—second lens, 3—third lens, 4—fourth lens, 5—fifth lens, 6—sixth lens, 7—seventh lens, 8—filter, A—front fixed group, B—zooming group, C—compensation group, D—rear fixed group, E—aperture, and F—detector. DETAILED DESCRIPTION

[0014] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0015] like Figure 1 As shown, in order to solve the shortcomings of the existing refrigerated medium-wave continuous zoom optical system, such as low resolution and small zoom ratio, the present invention discloses a 20x medium-wave continuous zoom optical lens with high resolution and large zoom ratio. From left to right along the propagation direction of the light, a first lens 1 with positive focal length as a front fixed group A, a second lens 2 with negative focal length as a zoom group B, a third lens 3 with positive focal length as a compensation group C, and a rear fixed group D composed of a fourth lens 4, a fifth lens 5, a sixth lens 6, and a seventh lens 7 are sequentially arranged along the propagation direction of the light. A filter 8 and a diaphragm E are sequentially arranged behind the rear fixed group D. Light from the object side converges through the lens group and is finally imaged on the target surface of the detector F. The focal length is changed by the linear movement of the zoom group B, and the image plane is stabilized by the nonlinear movement of the compensation group C, so that the total length remains unchanged. The zoom design is realized by the relative movement between the zoom group B and the compensation group C.

[0016] The first lens 1 is a meniscus aspheric lens with a convex surface bent toward the object side, the second lens 2 is a biconcave aspheric lens, the third lens 3 is a meniscus aspheric lens with a convex surface bent toward the image side, the fourth lens 4 is a meniscus biconvex lens with positive optical power, the fifth lens 5 is an aspheric lens with positive optical power and a convex surface bent toward the image side, the sixth lens 6 is an aspheric lens with positive optical power and a convex surface bent toward the image side, and the seventh lens 7 is an aspheric lens with positive optical power and a convex surface bent toward the object side.

[0017] The air spacing between the first lens 1 and the second lens 2 is L1±0.01mm, L1=13.74mm~52.22mm, the air spacing between the second lens 2 and the third lens 3 is L2±0.01mm, L2=120mm~5mm, the air spacing between the third lens 3 and the rear fixed group D (D1-D2-D3-D4) is L3±0.01mm, L3=23.49mm~100mm, the air spacing between the fourth lens 4 and the fifth lens 5 is 35.99±0.01mm, the air spacing between the fifth lens 5 and the sixth lens 6 is 8.89±0.01mm, and the air spacing between the sixth lens 6 and the seventh lens 7 is 10±0.01mm.

[0018] The material of the first lens 1 is silicon, and the center thickness is 9.95±0.01mm, the material of the second lens 2 is germanium, and the center thickness is 9±0.01mm, the center thickness of the third lens 3 is 5±0.01mm, and the material is silicon, the center thickness of the fourth lens 4 is 5.47±0.01mm, and the material is silicon, the center thickness of the fifth lens 5 is 3.1±0.01mm, and the material is germanium, the center thickness of the sixth lens 6 is 3.41±0.01mm, and the material is silicon, and the center thickness of the seventh lens 7 is 3.92±0.01mm, and the material is silicon.

[0019] The optical parameters of each lens in the optical system are shown in the following table.

[0020] .

[0021] In the above table, the two side surfaces of the first lens 1 are the first object side surface S1 and the first image side surface S2, the two side surfaces of the second lens 2 are the second object side surface S3 and the second image side surface S4, the two side surfaces of the third lens 3 are the third object side surface S5 and the third image side surface S6, the two side surfaces of the fourth lens 4 are the fourth object side surface S7 and the fourth image side surface S8, the two side surfaces of the fifth lens 5 are the fifth object side surface S9 and the fifth image side surface S10, the two side surfaces of the sixth lens 6 are the sixth object side surface S11 and the sixth image side surface S12, and the two side surfaces of the seventh lens 7 are the seventh object side surface S13 and the seventh image side surface S14.

[0022] The focal length of the compensation group C is generally controlled at 2.5 times the zoom group. If it is too long, the image plane compensation displacement will be too large. If it is too short, the relative aperture of the compensation group will be too large, making it difficult to correct aberrations. The aspheric equation used in the present invention is: , where c = 1 / R, R is the radius of curvature at the vertex of the aspheric surface, k is the cone coefficient, A4, A6, A8, A 10 is the aspheric coefficient. The aspheric coefficients of each side are shown in the following table.

[0023] .

[0024] The technical indicators of the optical system of the present invention are: the waveband is the mid-wave infrared waveband of 3.7μm to 4.8μm; the adapted pixel number is 640×512 and the pixel size is 15μm×15μm of the CCD or CMOS imaging device.

[0025] The optical system of the present invention in the short-focus, medium-focus and long-focus states is as follows Figure 2 to Figure 4 As shown, the maximum lens diameter is only 60mm, and the field of view transfer functions are as follows Figure 5 to Figure 7 As shown in the figure, at 17lp / mm, the MTF is greater than 0.3, and the maximum distortion at each focal length is less than 3%. Figure 8 to Figure 10 As shown, it has excellent imaging quality.

[0026] It should be understood that those skilled in the art can make improvements or changes based on the above description, and all these improvements and changes should fall within the scope of protection of the appended claims of the present invention.

Claims

1. A medium-wave continuous zoom refrigerated infrared lens, characterized in that: A first lens (1) with positive focal power, a second lens (2) with negative focal power, a third lens (3) with positive focal power, and a rear fixed group consisting of a fourth lens (4), a fifth lens (5), a sixth lens (6), and a seventh lens (7) are sequentially arranged along the propagation direction of light, and a filter (8) and an aperture (E) are sequentially arranged behind the rear fixed group; the first lens (1) is a meniscus aspheric lens with a convex surface curved toward the object side, the second lens (2) is a biconcave aspheric lens, the third lens (3) is a meniscus aspheric lens with a convex surface curved toward the image side, the fourth lens (4) is a meniscus biconvex lens with positive focal power, the fifth lens (5) is an aspheric lens with a positive focal power and a convex surface curved toward the image side, the sixth lens (6) is an aspheric lens with a positive focal power and a convex surface curved toward the image side, and the seventh lens (7) is an aspheric lens with a positive focal power and a convex surface curved toward the object side.

2. The medium-wave continuous zoom refrigerated infrared lens according to claim 1, characterized in that: The air interval between the first lens (1) and the second lens (2) is L1±0.01mm, L1=13.74mm-52.22mm, the air interval between the second lens (2) and the third lens (3) is L2±0.01mm, L2=120mm-5mm, the air interval between the third lens (3) and the rear fixed group is L3±0.01mm, L3=23.49mm-100mm, the air interval between the fourth lens (4) and the fifth lens (5) is 35.99±0.01mm, the air interval between the fifth lens (5) and the sixth lens (6) is 8.89±0.01mm, and the air interval between the sixth lens (6) and the seventh lens (7) is 10±0.01mm.

3. The medium-wave continuous zoom refrigerated infrared lens according to claim 2, characterized in that: The materials of the first lens (1), the second lens (2), the third lens (3), the fourth lens (4), the fifth lens (5), the sixth lens (6) and the seventh lens (7) are respectively silicon, germanium, silicon, silicon, germanium, silicon and silicon.

4. The medium-wave continuous zoom refrigerated infrared lens according to claim 2, characterized in that: The center thickness of the first lens (1) is 9.95±0.01 mm, the center thickness of the second lens (2) is 9±0.01 mm, the center thickness of the third lens (3) is 5±0.01 mm, the center thickness of the fourth lens (4) is 5.47±0.01 mm, the center thickness of the fifth lens (5) is 3.1±0.01 mm, the center thickness of the sixth lens (6) is 3.41±0.01 mm, and the center thickness of the seventh lens (7) is 3.92±0.01 mm.

5. A medium-wave continuous zoom refrigerated infrared lens according to claim 1, 2, 3 or 4, characterized in that: The focal length of the optical system is 15 to 300 mm, and the F number is 4; the adapted pixel number is 640×512, and the pixel size is 15 μm×15 μm of a CCD or CMOS imaging device.

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