An infrared medium and long wave dual-band optical system

Abstract

The present invention relates to an infrared medium and long wave dual-band optical system, which is composed of a positive power meniscus lens, a negative power meniscus lens, a positive power plano-convex lens, a diaphragm and an image plane arranged in sequence from the object side to the image side along the optical axis; the front and rear surfaces of the positive power meniscus lens and the negative power meniscus lens are both spherical surfaces; the front surface of the positive power plano-convex lens L3 is a spherical surface, and the rear surface is a harmonic diffraction surface. The present invention adopts a common aperture and confocal structure, which can better correct chromatic aberration and monochromatic aberration in a wide wavelength band range, and has a simple structure and is easy to assemble and align.

Description

Technical Field

[0001] The present invention belongs to the technical field of imaging optical system design, and particularly relates to an infrared medium and long wave dual-band optical system. Background Art

[0002] Most traditional infrared optical systems are single-band systems. The single working band, combined with factors such as the camouflage of targets and the diversity of environments, will inevitably lead to certain limitations in the information acquisition of the system. Infrared multi-band optical systems have better detection / imaging capabilities than single-band systems. Currently, infrared multi-band optical systems mainly adopt three configurations, namely, split-aperture combined structure, common-aperture split-beam structure, and common-aperture confocal structure. Among them, the common-aperture confocal structure can overcome the influence of the beam-splitting element on the system, has a simple structure, is relatively easy to process and align, can also reduce costs, and at the same time ensures the transmittance and stability of the system. However, the number of infrared materials that can transmit a wide spectral range is limited, and the choice of materials is small. Therefore, the design difficulty of the common-aperture confocal infrared multi-band optical system is how to correct chromatic aberration and other monochromatic aberrations in different bands simultaneously.

[0003] The thermal sensitivity of most infrared optical materials is much higher than that of visible light optical materials. With the change of environmental temperature, the refractive index of infrared optical materials and the geometric dimensions of components are more likely to change. Subsequently, the thermal defocus caused by the drift of the image plane of the system will deteriorate the imaging quality. Therefore, the athermal design of infrared optical systems is crucial. Currently, among several athermalization technologies, the optical passive athermalization technology has the simplest structure and does not require any additional focusing mechanism, which is particularly suitable for the miniaturization and lightweight design of modern infrared optoelectronic systems. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide an infrared medium and long wave dual-band optical system. The working band of this optical system covers the infrared medium wave and long wave spectral regions, can better correct chromatic aberration in a wide band range, and has a simple structure and is easy to align.

[0005] To solve the above technical problem, the infrared medium and long wave dual-band optical system of the present invention is composed of a positive power meniscus lens, a negative power meniscus lens, a positive power plano-convex lens, a diaphragm, and an image plane arranged in sequence from the object side to the image side along the optical axis; the front and rear surfaces of the positive power meniscus lens and the negative power meniscus lens are both spherical surfaces; the front surface of the positive power plano-convex lens is a spherical surface, and the rear surface is a harmonic diffraction surface.

[0006] Further, the front and rear surface curvature radii of the positive meniscus lens are 50.00 - 60.00 mm and 106.12 - 162.53 mm respectively; the front and rear surface curvature radii of the negative meniscus lens are 120.14 - 185.27 mm and 67.51 - 89.64 mm respectively; the front surface curvature radius of the positive plano-convex lens is 445.30 - 490.00 mm.

[0007] Further, the central thickness of the positive meniscus lens is 5.5 - 6.0 mm; the central thickness of the negative meniscus lens is 5.5 - 6.0 mm; the central thickness of the positive plano-convex lens is 1.8 - 1.9 mm.

[0008] Further, the central air gap between the positive meniscus lens and the negative meniscus lens is 0.68 - 0.72 mm; the central air gap between the negative meniscus lens and the positive plano-convex lens is 38.0 - 38.6 mm.

[0009] The central air gap between the positive plano-convex lens and the diaphragm is 5.0 - 5.8 mm; the central air gap between the diaphragm and the image plane is 19.0 mm.

[0010] Further, the harmonic diffraction surface on the rear surface of the positive plano-convex lens satisfies the following relationship:

[0011]

[0012]

[0013] where f1 is the focal length in the mid-wave infrared band; λ1 is the central wavelength in the mid-wave infrared band; f2 is the focal length in the long-wave infrared band; λ2 is the central wavelength in the long-wave infrared band; p is the phase depth factor; m is an integer.

[0014] Further, for the harmonic diffraction surface on the rear surface of the positive plano-convex lens, the phase depth factor P is 2, the diffraction order HOR corresponding to the mid-wave infrared band is 5, the diffraction order HOR corresponding to the long-wave infrared band is 2, the normalized radius NormRadius is 4.9 mm for both, and the diffraction surface coefficients C1 are -1.554 to -1.261, C2 are 0.526 to 1.666, and C3 are -0.269 to -0.255 for both.

[0015] Further, the material of the positive meniscus lens is silicon; the material of the negative meniscus lens is germanium; the material of the positive plano-convex lens is a chalcogenide glass material.

[0016] The beneficial effects of the present invention are as follows: The optical system adopts a common-aperture confocal structure, which can image targets in different bands without any adjustment; The optical passive athermalization technology is adopted, and the applicable environmental temperature range can reach -80°C to 100°C, and no additional focusing is required when imaging at any temperature; The optical system only uses 3 lenses, with a simple structure and easy to assemble and align. A harmonic diffraction surface is introduced on the planar substrate, which is easier to process and manufacture than the ordinary diffraction surface, which is beneficial to cost savings, and the harmonic diffraction surface can make the theoretical diffraction efficiencies of multiple wavelengths approximate 100% at the same time; The optical system can better correct chromatic aberration in the mid-wave and long-wave infrared bands, and realizes the correction of secondary spectrum, and has excellent image quality in different working environments, and the image plane has good thermal stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a schematic structural diagram of the mid-wave and long-wave infrared dual-band optical system of the present invention;

[0018] Figure 2 is a modulation transfer function curve graph of the mid-wave band imaging of Embodiment 1 of the mid-wave and long-wave infrared dual-band optical system of the present invention at 20°C;

[0019] Figure 3 is a modulation transfer function curve graph of the long-wave band imaging of Embodiment 1 of the mid-wave and long-wave infrared dual-band optical system of the present invention at 20°C;

[0020] Figure 4 is a longitudinal aberration curve graph of the mid-wave band imaging of Embodiment 1 of the mid-wave and long-wave infrared dual-band optical system of the present invention at 20°C;

[0021] Figure 5 is a longitudinal aberration curve graph of the long-wave band imaging of Embodiment 1 of the mid-wave and long-wave infrared dual-band optical system of the present invention at 20°C;

[0022] Figure 6 is a distortion curve graph of the mid-wave band imaging of Embodiment 1 of the mid-wave and long-wave infrared dual-band optical system of the present invention at 20°C;

[0023] Figure 7 is a distortion curve graph of the long-wave band imaging of Embodiment 1 of the mid-wave and long-wave infrared dual-band optical system of the present invention at 20°C;

[0024] Figure 8 is a modulation transfer function curve graph of the mid-wave band imaging of Embodiment 1 of the mid-wave and long-wave infrared dual-band optical system of the present invention at -80°C;

[0025] Figure 9 is a modulation transfer function curve graph of the long-wave band imaging of Embodiment 1 of the mid-wave and long-wave infrared dual-band optical system of the present invention at -80°C;

[0026] Figure 10 It is the modulation transfer function curve graph of the mid-wave band imaging of Embodiment 1 of the infrared mid-long wave dual-band optical system of the present invention at 100 °C;

[0027] Figure 11 It is the modulation transfer function curve graph of the long-wave band imaging of Embodiment 1 of the infrared mid-long wave dual-band optical system of the present invention at 100 °C;

[0028] Figure 12 It is the longitudinal aberration curve graph of the mid-wave band imaging of Embodiment 1 of the infrared mid-long wave dual-band optical system of the present invention at -80 °C;

[0029] Figure 13 It is the longitudinal aberration curve graph of the long-wave band imaging of Embodiment 1 of the infrared mid-long wave dual-band optical system of the present invention at -80 °C;

[0030] Figure 14 It is the longitudinal aberration curve graph of the mid-wave band imaging of Embodiment 1 of the infrared mid-long wave dual-band optical system of the present invention at 100 °C;

[0031] Figure 15 It is the longitudinal aberration curve graph of the long-wave band imaging of Embodiment 1 of the infrared mid-long wave dual-band optical system of the present invention at 100 °C;

[0032] Figure 1 Wherein: L1 is a positive power meniscus lens, L2 is a negative power meniscus lens, L3 is a positive power plano-convex lens, 1 is a diaphragm; 2 is an image plane. Detailed implementation manners

[0033] The present invention will be further described in detail below with reference to the drawings and embodiments.

[0034] As Figure 1 shown, the infrared mid-long wave dual-band optical system of the present invention is composed of a positive power meniscus lens L1, a negative power meniscus lens L2, a positive power plano-convex lens L3, a diaphragm 1 and an image plane 2 which are sequentially arranged from the object side to the image side along the optical axis; the convex surface of the positive power meniscus lens L1 faces the object side, and both the front and rear surfaces are spherical surfaces; the convex surface of the negative power meniscus lens L2 faces the object side, and both the front and rear surfaces are spherical surfaces; the convex surface of the positive power plano-convex lens L3 faces the object side, the plane faces the image side, the front surface is a spherical surface, and the rear surface is a harmonic diffraction surface.

[0035] When the material of the positive meniscus lens L1 with positive optical power is silicon, the material of the negative meniscus lens L2 with negative optical power is germanium, and the material of the positive plano-convex lens L3 with positive optical power is chalcogenide glass materials such as IRG206, IRG207, IRG205, IRG201, etc., the environmental temperature range adapted by the optical system can reach -80°C to 100°C, and no additional focusing is required when imaging at any temperature.

[0036] For the harmonic diffraction surface adopted on the rear surface of the positive plano-convex lens L3 with positive optical power, the relationship between the designed wavelength and the focal length corresponding to different wavelength bands satisfies the following relational formula:

[0037]

[0038] Among them, f1 is the focal length in the mid-wave infrared band; λ1 is the central wavelength in the mid-wave infrared band; f2 is the focal length in the long-wave infrared band; λ2 is the central wavelength in the long-wave infrared band; p is the phase depth factor, and preferably P is equal to 2; m is an integer.

[0039] Light waves in different wavelength bands can converge to a common focal point, and the harmonic diffraction surface needs to satisfy the following resonance conditions:

[0040]

[0041] For the infrared mid-wave and long-wave dual-band optical system of the present invention, the surface profile of the harmonic diffraction surface of the positive plano-convex lens L3 satisfies the following relational formula:

[0042]

[0043] Among them, Z(r) is the distance sagitta from the vertex of the aspheric surface along the optical axis at the position with height r; c is the curvature of the aspheric surface, where c = 1 / R, and R is the radius of curvature of the aspheric surface; k is the conic coefficient; A, B, C, D are aspheric coefficients; HOR is the diffraction order, the diffraction order HOR corresponding to the mid-wave infrared band is 5, and the diffraction order HOR corresponding to the long-wave infrared band is 2; C1, C2, C3 are diffraction surface coefficients, λ0 is the designed central wavelength, n is the refractive index of the positive plano-convex lens L3, and n0 is the refractive index of air.

[0044] Example 1:

[0045] The specific parameters of each lens are shown in Table 1-1.

[0046] Table 1-1

[0047]

[0048] The optical parameters of the harmonic diffraction surface are shown in Table 1-2.

[0049] Table 1-2

[0050]

[0051]

[0052] In this embodiment, the working bands of the infrared medium and long wave dual-band optical system are 3.7 - 4.3μm and 9 - 11μm. The central wavelength within the 3.7 - 4.3μm band is 4μm, and the central wavelength within the 9 - 11μm band is 10μm. The phase depth factor p is 2, the effective focal length is 71mm, the F number is 2.36, the maximum half field of view angle of the diagonal is 2.5°, and the operating temperature is -80°C to 100°C.

[0053] As Figure 2 shown is the modulation transfer function curve of the optical system in the medium wave band at 20°C in this embodiment. The modulation transfer function curves of different fields of view are all close to the diffraction limit, and the modulation transfer function values are all better than 0.71, meeting the requirements of the optical system for resolution.

[0054] As Figure 3 shown is the modulation transfer function curve of the optical system in the long wave band at 20°C in this embodiment. The modulation transfer function curves of different fields of view are all close to the diffraction limit, and the modulation transfer function values are all better than 0.33, meeting the requirements of the optical system for resolution.

[0055] As Figure 4 shown is the longitudinal aberration curve of the optical system in the medium wave band at 20°C in this embodiment. The chromatic aberration correction of different aperture bands within the entire spectral range is good, and the correction of the secondary spectrum is achieved.

[0056] As Figure 5 shown is the longitudinal aberration curve of the optical system in the long wave band at 20°C in this embodiment. The chromatic aberration correction of different aperture bands within the entire spectral range is good, and the correction of the secondary spectrum is achieved.

[0057] As Figure 6 shown is the distortion curve of the optical system in the medium wave band at 20°C in this embodiment. The distortion of the full field of view at wavelengths 3.7μm, 4μm, and 4.3μm is less than 0.31%, and the fidelity is good, fully meeting the requirements of the optical system for distortion.

[0058] As Figure 7 shown is the distortion curve of the optical system in the long wave band at 20°C in this embodiment. The distortion of the full field of view at wavelengths 9μm, 10μm, and 11μm is less than 0.32%, and the fidelity is good, fully meeting the requirements of the optical system for distortion.

[0059] As Figure 8The modulation transfer function curve of the optical system of this embodiment for mid-wave band imaging at -80°C is shown. The modulation transfer function curves for different fields of view are all close to the diffraction limit, and the modulation transfer function values are all better than 0.63, meeting the resolution requirements of the optical system.

[0060] As Figure 9 The modulation transfer function curve of the optical system of this embodiment for long-wave band imaging at -80°C is shown. The modulation transfer function curves for different fields of view are all close to the diffraction limit, and the modulation transfer function values are all better than 0.32, meeting the resolution requirements of the optical system.

[0061] As Figure 10 The modulation transfer function curve of the optical system of this embodiment for mid-wave band imaging at 100°C is shown. The modulation transfer function curves for different fields of view are all close to the diffraction limit, and the modulation transfer function values are all better than 0.70, meeting the resolution requirements of the optical system.

[0062] As Figure 11 The modulation transfer function curve of the optical system of this embodiment for long-wave band imaging at 100°C is shown. The modulation transfer function curves for different fields of view are all close to the diffraction limit, and the modulation transfer function values are all better than 0.32, meeting the resolution requirements of the optical system.

[0063] As Figure 12 The longitudinal aberration curve of the optical system of this embodiment for mid-wave band imaging at -80°C is shown. The chromatic aberration of different aperture bands is well corrected within the entire spectral range, and the secondary spectrum is corrected.

[0064] As Figure 13 The longitudinal aberration curve of the optical system of this embodiment for long-wave band imaging at -80°C is shown. The chromatic aberration of different aperture bands is well corrected within the entire spectral range, and the secondary spectrum is corrected.

[0065] As Figure 14 The longitudinal aberration curve of the optical system of this embodiment for mid-wave band imaging at 100°C is shown. The chromatic aberration of different aperture bands is well corrected within the entire spectral range, and the secondary spectrum is corrected.

[0066] As Figure 15 The longitudinal aberration curve of the optical system of this embodiment for long-wave band imaging at 100°C is shown. The chromatic aberration of different aperture bands is well corrected within the entire spectral range, and the secondary spectrum is corrected.

[0067] Example 2:

[0068] The specific parameters of each lens are shown in Table 2-1.

[0069] Table 2-1

[0070]

[0071] The optical parameters of the harmonic diffraction surface are shown in Table 2-2.

[0072] Table 2-2

[0073] Wavelength Band (μm) k A B C HOR Norm Radius (mm) <![CDATA[C1]]> <![CDATA[C2]]> <![CDATA[C3]]> 3.7～4.3 0 0 0 0 5 4.9 -1.554 0.526 -0.269 9～11 0 0 0 0 2 4.9 -1.554 0.526 -0.269

[0074] In this embodiment, the working bands of the infrared medium and long wave dual-band optical system are 3.7 - 4.3 μm and 9 - 11 μm. The central wavelengths within the 3.7 - 4.3 μm band are 4 μm, and the central wavelengths within the 9 - 11 μm band are 10 μm. The phase depth factor p is 2, the effective focal length is 71 mm, the F number is 2.36, the maximum half field angle of the diagonal is 2.5°, and the working temperature is -80°C to 100°C.

[0075] The optical system of this embodiment images in the medium wave and long wave bands at 20°C, and the modulation transfer function values are respectively better than 0.51 and 0.29, meeting the requirements of the optical system for resolution; the chromatic aberration correction of different aperture bands within the entire spectral range is good, and the correction of the secondary spectrum is achieved; the distortion of the full field of view at wavelengths 3.7 μm, 4 μm, and 4.3 μm is less than 0.1%, and the distortion of the full field of view at wavelengths 9 μm, 10 μm, and 11 μm is less than 0.1%, with good fidelity, fully meeting the requirements of the optical system for distortion.

[0076] The optical system of this embodiment images in the medium wave and long wave bands at -80°C, and the modulation transfer function values are respectively better than 0.35 and 0.28, meeting the requirements of the optical system for resolution; the chromatic aberration correction of different aperture bands within the entire spectral range is good, and the correction of the secondary spectrum is achieved.

[0077] The optical system of this embodiment images in the medium wave and long wave bands at 100°C, and the modulation transfer function values are respectively better than 0.40 and 0.31, meeting the requirements of the optical system for resolution; the chromatic aberration correction of different aperture bands within the entire spectral range is good, and the correction of the secondary spectrum is achieved.

[0078] Embodiment 3:

[0079] The specific parameters of each lens are shown in Table 3-1.

[0080] Table 3-1

[0081]

[0082] The optical parameters of the harmonic diffraction surface are shown in Table 3-2.

[0083] Table 3-2

[0084] Wavelength Band (μm) k A B C HOR Norm Radius (mm) <![CDATA[C1]]> <![CDATA[C2]]> <![CDATA[C3]]> 3.7～4.3 0 0 0 0 5 4.9 -1.261 1.666 -0.255 9～11 0 0 0 0 2 4.9 -1.261 1.666 -0.255

[0085] In this embodiment, the working bands of the infrared medium-long wave dual-band optical system are 3.7 - 4.3 μm and 9 - 11 μm. The central wavelength within the 3.7 - 4.3 μm band is 4 μm, and the central wavelength within the 9 - 11 μm band is 10 μm. The phase depth factor p is 2, the effective focal length is 71 mm, the F number is 2.36, the maximum half field of view angle of the diagonal is 2.5°, and the operating temperature is -80°C to 100°C.

[0086] The optical system of this embodiment images in the medium wave and long wave bands at 20°C, and the modulation transfer function values are respectively better than 0.55 and 0.26, meeting the requirements of the optical system for resolution; the chromatic aberration correction of different aperture bands within the entire spectral range is good, and the correction of the secondary spectrum is achieved; the distortion of the full field of view at wavelengths of 3.7 μm, 4 μm, and 4.3 μm is less than 0.51%, and the distortion of the full field of view at wavelengths of 9 μm, 10 μm, and 11 μm is less than 0.51%, with good fidelity, fully meeting the requirements of the optical system for distortion.

[0087] The optical system of this embodiment images in the medium wave and long wave bands at -80°C, and the modulation transfer function values are respectively better than 0.49 and 0.24, meeting the requirements of the optical system for resolution; the chromatic aberration correction of different aperture bands within the entire spectral range is good, and the correction of the secondary spectrum is achieved.

[0088] The optical system of this embodiment images in the medium wave and long wave bands at 100°C, and the modulation transfer function values are respectively better than 0.52 and 0.25, meeting the requirements of the optical system for resolution; the chromatic aberration correction of different aperture bands within the entire spectral range is good, and the correction of the secondary spectrum is achieved.

[0089] Example 4:

[0090] The specific parameters of each lens are shown in Table 4 - 1.

[0091] Table 4 - 1

[0092]

[0093]

[0094] The optical parameters of the harmonic diffraction surface are shown in Table 4 - 2.

[0095] Table 4 - 2

[0096] Wavelength Band (μm) k A B C HOR Norm Radius (mm) <![CDATA[C1]]> <![CDATA[C2]]> <![CDATA[C3]]> 3.7～4.3 0 0 0 0 5 4.9 -1.272 1.601 -0.262 9～11 0 0 0 0 2 4.9 -1.272 1.601 -0.262

[0097] In this embodiment, the working bands of the infrared medium- and long-wave dual-band optical system are 3.7 - 4.3 μm and 9 - 11 μm. The central wavelength within the 3.7 - 4.3 μm band is 4 μm, and the central wavelength within the 9 - 11 μm band is 10 μm. The phase depth factor p is 2, the effective focal length is 71 mm, the F number is 2.36, the maximum half field of view angle of the diagonal is 2.5°, and the operating temperature is -80°C to 100°C.

[0098] The optical system of this embodiment images in the medium-wave and long-wave bands at 20°C. The modulation transfer function curves of different fields of view are all close to the diffraction limit, and the modulation transfer function values are respectively better than 0.71 and 0.31, meeting the requirements of the optical system for resolution; the chromatic aberration correction of different aperture bands within the entire spectral range is good, and the correction of the secondary spectrum is achieved; the distortion of the full field of view at wavelengths 3.7 μm, 4 μm, and 4.3 μm is less than 0.26%, and the distortion of the full field of view at wavelengths 9 μm, 10 μm, and 11 μm is less than 0.27%, with good fidelity, fully meeting the requirements of the optical system for distortion;

[0099] The optical system of this embodiment images in the medium-wave and long-wave bands at -80°C. The modulation transfer function curves of different fields of view are all close to the diffraction limit, and the modulation transfer function values are respectively better than 0.70 and 0.29, meeting the requirements of the optical system for resolution; the chromatic aberration correction of different aperture bands within the entire spectral range is good, and the correction of the secondary spectrum is achieved.

[0100] The optical system of this embodiment images in the medium-wave and long-wave bands at 100°C. The modulation transfer function curves of different fields of view are all close to the diffraction limit, and the modulation transfer function values are respectively better than 0.71 and 0.31, meeting the requirements of the optical system for resolution; the chromatic aberration correction of different aperture bands within the entire spectral range is good, and the correction of the secondary spectrum is achieved.

[0101] Embodiment 5:

[0102] The specific parameters of each lens are shown in Table 5-1.

[0103] Table 5-1

[0104]

[0105]

[0106] The optical parameters of the harmonic diffraction surface are shown in Table 5-2.

[0107] Table 5-2

[0108] Wavelength Band (μm) k A B C HOR Norm Radius (mm) <![CDATA[C1]]> <![CDATA[C2]]> <![CDATA[C3]]> 3.7～4.3 0 0 0 0 5 4.9 -1.263 1.666 -0.258 9～11 0 0 0 0 2 4.9 -1.263 1.666 -0.258

[0109] In this embodiment, the working bands of the infrared medium and long wave dual-band optical system are 3.7 - 4.3 μm and 9 - 11 μm. The central wavelength within the 3.7 - 4.3 μm band is 4 μm, and the central wavelength within the 9 - 11 μm band is 10 μm. The phase depth factor p is 2, the effective focal length is 71 mm, the F number is 2.36, the maximum half field of view angle of the diagonal is 2.5°, and the operating temperature is -80°C to 100°C.

[0110] The optical system of this embodiment images in the medium wave and long wave bands at 20°C. The modulation transfer function curves of different fields of view are all close to the diffraction limit, and the modulation transfer function values are respectively better than 0.70 and 0.31, meeting the requirements of the optical system for resolution; the chromatic aberration correction of different aperture bands within the entire spectral range is good, and the correction of the secondary spectrum is achieved; the distortion of the full field of view at wavelengths 3.7 μm, 4 μm, and 4.3 μm is less than 0.26%, and the distortion of the full field of view at wavelengths 9 μm, 10 μm, and 11 μm is less than 0.28%, with good fidelity, fully meeting the requirements of the optical system for distortion;

[0111] The optical system of this embodiment images in the medium wave and long wave bands at -80°C. The modulation transfer function curves of different fields of view are all close to the diffraction limit, and the modulation transfer function values are respectively better than 0.68 and 0.30, meeting the requirements of the optical system for resolution; the chromatic aberration correction of different aperture bands within the entire spectral range is good, and the correction of the secondary spectrum is achieved.

[0112] The optical system of this embodiment images in the medium wave and long wave bands at 100°C. The modulation transfer function curves of different fields of view are all close to the diffraction limit, and the modulation transfer function values are respectively better than 0.67 and 0.31, meeting the requirements of the optical system for resolution; the chromatic aberration correction of different aperture bands within the entire spectral range is good, and the correction of the secondary spectrum is achieved.

[0113] Embodiment 6:

[0114] The specific parameters of each lens are shown in Table 6-1.

[0115] Table 6-1

[0116]

[0117] The optical parameters of the harmonic diffraction surface are shown in Table 6-2.

[0118] Table 6-2

[0119] Wavelength Band (μm) k A B C HOR Norm Radius (mm) <![CDATA[C1]]> <![CDATA[C2]]> <![CDATA[C3]]> 3.7～4.3 0 0 0 0 5 4.9 -1.272 1.621 -0.258 9～11 0 0 0 0 2 4.9 -1.272 1.621 -0.258

[0120] In this embodiment, the working bands of the infrared mid-long wave dual-band optical system are 3.7 - 4.3 μm and 9 - 11 μm. The central wavelength within the 3.7 - 4.3 μm band is 4 μm, and the central wavelength within the 9 - 11 μm band is 10 μm. The phase depth factor p is 2, the effective focal length is 71 mm, the F number is 2.36, the maximum half field of view angle of the diagonal is 2.5°, and the operating temperature is -80°C to 100°C.

[0121] The optical system of this embodiment images in the mid-wave and long-wave bands at 20°C. The modulation transfer function curves of different fields of view are all close to the diffraction limit, and the modulation transfer function values are respectively better than 0.71 and 0.31, meeting the requirements of the optical system for resolution; the chromatic aberration correction of different aperture bands within the entire spectral range is good, and the correction of the secondary spectrum is achieved; the distortion of the full field of view is less than 0.27% at wavelengths of 3.7 μm, 4 μm, and 4.3 μm, and the distortion of the full field of view is less than 0.28% at wavelengths of 9 μm, 10 μm, and 11 μm, with good fidelity, fully meeting the requirements of the optical system for distortion;

[0122] The optical system of this embodiment images in the mid-wave and long-wave bands at -80°C. The modulation transfer function curves of different fields of view are all close to the diffraction limit, and the modulation transfer function values are respectively better than 0.69 and 0.30, meeting the requirements of the optical system for resolution; the chromatic aberration correction of different aperture bands within the entire spectral range is good, and the correction of the secondary spectrum is achieved.

[0123] The optical system of this embodiment images in the mid-wave and long-wave bands at 100°C. The modulation transfer function curves of different fields of view are all close to the diffraction limit, and the modulation transfer function values are respectively better than 0.70 and 0.31, meeting the requirements of the optical system for resolution; the chromatic aberration correction of different aperture bands within the entire spectral range is good, and the correction of the secondary spectrum is achieved.

[0124] The present invention is not limited to the above embodiments. When other optical materials are used for each lens, good imaging effects can be obtained at room temperature.

Claims

1. An infrared medium and long wave dual-band optical system, characterized in that It is composed of a positive meniscus lens, a negative meniscus lens, a positive plano-convex lens, a diaphragm and an image plane, which are sequentially arranged from the object side to the image side along the optical axis; the front and rear surfaces of the positive meniscus lens and the negative meniscus lens are both spherical surfaces; the front surface of the positive plano-convex lens is a spherical surface, and the rear surface is a harmonic diffraction surface; the front and rear surface curvature radii of the positive meniscus lens are 50.00 - 60.00 mm and 106.12 - 162.53 mm respectively; the front and rear surface curvature radii of the negative meniscus lens are 120.14 - 185.27 mm and 67.51 - 89.64 mm respectively; the front surface curvature radius of the positive plano-convex lens is 445.30 - 490.00 mm; the central thickness of the positive meniscus lens is 5.5 - 6.0 mm; the central thickness of the negative meniscus lens is 5.5 - 6.0 mm; the central thickness of the positive plano-convex lens is 1.8 - 1.9 mm; the central air gap between the positive meniscus lens and the negative meniscus lens is 0.68 - 0.72 mm; the central air gap between the negative meniscus lens and the positive plano-convex lens is 38.0 - 38.6 mm; the harmonic diffraction surface on the rear surface of the positive plano-convex lens satisfies the following relationship: Where, f1 is the focal length in the mid-wave infrared band; λ1 is the central wavelength in the mid-wave infrared band; f2 is the focal length in the long-wave infrared band; λ2 is the central wavelength in the long-wave infrared band; p is the phase depth factor; m is an integer; for the harmonic diffraction surface on the rear surface of the positive plano-convex lens, the phase depth factor P is 2, the diffraction order HOR corresponding to the mid-wave infrared band is 5, the diffraction order HOR corresponding to the long-wave infrared band is 2, the normalized radius Norm Radius is 4.9 mm for both, and the diffraction surface coefficients C1 are -1.554 to -1.261, C2 are 0.526 to 1.666, and C3 are -0.269 to -0.255 for both; the material of the positive meniscus lens is silicon; the material of the negative meniscus lens is germanium; the material of the positive plano-convex lens is a chalcogenide glass material.

2. The infrared medium and long wave dual-band optical system according to claim 1, wherein The central air gap between the positive plano-convex lens and the diaphragm is 5.0 - 5.8 mm; the central air gap between the diaphragm and the image plane is 19.0 mm.

Images