A middle-long wave refrigeration dual-band harmonic diffraction lens

Abstract

The utility model relates to optical technology field especially relates to a middle long wave refrigeration double wave band harmonic diffraction lens, including first lens, second lens, third lens and refrigeration detector, the utility model discloses through setting first lens, second lens, third lens and refrigeration detector, wherein the refrigeration detector is composed of window, cold screen, cold diaphragm and imaging focal plane, and it is sequentially arranged according to the direction from object side to image side, can constitute the middle long wave refrigeration double wave band harmonic diffraction lens of adaptation resolution 640x512, image element size is 15 microns, the total length of optical system reaches 138.42mm, the maximum aperture reaches 96mm, the imaging quality under two wave bands is good, and the compact structure can utilize the special dispersion principle of harmonic diffraction optical element, produces different diffraction effects under different wavelengths, realizes the accurate control to different wave band light, thereby can reduce aberration, and effectively corrects aberration on wide wave band.

Description

Technical Field

[0001] This utility model relates to the field of optical technology, and in particular to a medium- and long-wavelength cooled dual-band harmonic diffraction lens. Background Technology

[0002] As cooled infrared detectors become more mature, in order to meet the needs of different applications, such as gas detection and aerospace, dual-band cooled detectors that can respond to both mid-wave and long-wave infrared have been developed. Mid-wave and long-wave cooled dual-band detectors are mainly used to perform high-performance imaging in both mid-wave and long-wave infrared bands at the same time, so as to reduce the false alarm rate and meet the target detection requirements in complex backgrounds. Their working spectrum covers two ranges: 3.7μm~4.8μm and 7.7μm~9.6μm. Therefore, an optical system capable of responding to such a wide spectrum is required.

[0003] Existing mid-wave and long-wave cooled dual-band detectors often suffer from poor imaging quality when simultaneously capturing mid-wave and long-wave infrared information due to their wide band range, and it is difficult to improve the imaging quality of both bands simultaneously through a single correction method.

[0004] Therefore, to address the problem that existing medium- and long-wavelength cooled dual-band detectors often have difficulty simultaneously correcting aberrations across a wide spectral band, a medium- and long-wavelength cooled dual-band harmonic diffraction lens can be designed. By utilizing the special dispersion principle of harmonic diffraction optical elements, different diffraction effects are generated at different wavelengths, enabling precise control of light in different bands, reducing aberrations, and thus effectively correcting aberrations across a wide spectral band. Utility Model Content

[0005] To overcome the problem that existing medium- and long-wave cooled dual-band detectors typically have wide spectral band aberrations that are difficult to correct simultaneously.

[0006] The technical solution of this utility model is: a medium-long wave cooled dual-band harmonic diffraction lens, including a first lens, a second lens, a third lens and a cooled detector, wherein the second lens, the third lens and the cooled detector are arranged sequentially from the object side to the image side along the optical axis.

[0007] Preferably, the cooled detector includes a detector protection window, a cold screen, a cold aperture, and a focal plane. The cooled detector is encapsulated within the protection window. The cold screen is located in front of the photosensitive area of ​​the cooled detector, the cold aperture is located in front of the cold screen, and the focal plane is located at the rear end of the entire optical system and is adjacent to the cold screen and the cold aperture.

[0008] Preferably, the first lens is a meniscus silicon positive lens with its convex surface facing the object side, and it has an aspherical surface on it; Preferably, the second lens is a biconcave germanium negative lens with a harmonic diffraction surface. Preferably, the third lens is a meniscus silicon positive lens with its convex surface facing the object side and an aspherical surface thereon.

[0009] The beneficial effects of this utility model are: 1. By setting up a first lens, a second lens, a third lens, and a cooled detector, wherein the cooled detector consists of a window, a cold screen, a cold aperture, and an imaging focal plane, and arranged sequentially from the object side to the image side, a medium-to-long-wavelength cooled dual-band harmonic diffraction lens with a resolution of 640x512 and a pixel size of 15 micrometers can be formed. The total length of the optical system is 138.42 mm, and the maximum aperture is 96 mm. The imaging quality in both bands is good, and the structure is compact. It can utilize the special dispersion principle of harmonic diffraction optical elements to produce different diffraction effects at different wavelengths, thereby achieving precise control of light in different bands, reducing aberrations, and effectively correcting aberrations over a wide band. Attached Figure Description

[0010] Figure 1 The diagram shown is of the optical system of the medium-long wave cooled dual-band harmonic diffraction lens of this utility model; Figure 2 The figure shown is the mid-wave optical transfer function diagram of the mid-long wave cooled dual-band harmonic diffraction lens of this utility model; Figure 3 The image shown is a mid-wavelength point array diagram of the medium- and long-wavelength cooled dual-band harmonic diffraction lens of this utility model. Figure 4 The image shown is a wave image distortion diagram of the medium-long wave cooled dual-band harmonic diffraction lens of this utility model. Figure 5 The diagram shown is the long-wave optical transfer function of the medium-long wave cooled dual-band harmonic diffraction lens of this utility model. Figure 6 The image shown is a long-wave dot plot of the medium-long wave cooled dual-band harmonic diffraction lens of this utility model. Figure 7 The image shown is a long-wave astigmatic distortion diagram of the medium- and long-wave cooled dual-band harmonic diffraction lens of this utility model.

[0011] Explanation of reference numerals in the attached drawings: 110, first lens; 120, second lens; 130, third lens; 210, cooled detector; 212, detector protection window; 214, cold screen; 216, cold aperture; 218, focal plane; S1-S6, various surfaces of the lens. Detailed Implementation

[0012] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0013] Please see Figure 1This utility model provides an embodiment: a medium-to-long-wavelength cooled dual-band harmonic diffraction lens, including a first lens 110, a second lens 120, a third lens 130, and a cooled detector 210. The second lens 120, the third lens 130, and the cooled detector 210 are arranged sequentially along the optical axis from the object side to the image side. The cooled detector 210 includes a detector protection window 212, a cold screen 214, a cold aperture 216, and a focal plane 218. The cooled detector 210 is encapsulated within the detector protection window 212. Within 12, the cold screen 214 is located at the front end of the photosensitive area of ​​the cooled detector 210, the cold aperture 216 is located in front of the cold screen 214, and the focal plane 218 is located at the rear end of the entire optical system and is adjacent to the cold screen 214 and the cold aperture 216. The first lens 110 is a meniscus positive silicon lens with its convex surface facing the object side and has an aspherical surface on it; the second lens 120 is a biconcave germanium negative lens with a resonant diffraction surface on it; and the third lens 130 is a meniscus positive silicon lens with its convex surface facing the object side and has an aspherical surface on it.

[0014] Please see Figures 2-7 In this embodiment, the following parameters are satisfied: EFL = 100mm, F-number = 2.0, total length of the optical system (including the cooled detector 210) = 138.42mm, adapter detector 640x512, pixel size 15μm, horizontal field of view of the lens is 2ω = 5.5°, and the aspherical surfaces in the lens satisfy the following expression:

[0015] Where z is the distance vector from the vertex of the aspherical surface at a height of r along the optical axis, c represents the vertex curvature of the surface, k is the conic coefficient, and α2, α3, α4, α5, and α6 are higher-order aspherical coefficients. The diffraction surface in the lens lens satisfies the following expression: Ф=M(A1ρ 2 +A2ρ 4 ), where M is the diffraction order and Ф is the phase of the diffraction plane. , A1 and A2 are the planned radius of the diffraction surface and the phase coefficients of the diffraction surface.

[0016] When working, light first shines on the first lens 110, and is initially focused by the first lens 110 to converge the diverging light into a smaller area; Then the light shines on the second lens 120, and the visible light is reflected by the second lens 120 and the mid-to-long-wave infrared light is transmitted. The reflected visible light part will continue to pass through the transmission element for aberration correction to ensure the quality of the image on the detection surface. The transmitted infrared light then enters the third lens 130. The third lens 130 achieves dual-band achromaticity through its harmonic diffraction hybrid optical element, that is, it ensures that the light in the mid-wave infrared and long-wave infrared bands can be clearly focused on the detector. The harmonic diffraction surface microstructure plays a key role here. It makes the two center wavelengths in the infrared dual bands located at the two harmonic wavelength positions, and resonates at the first and second diffraction orders. The two diffraction orders have the same optical power, thereby achieving confocal achromaticity in the infrared dual bands. Finally, the light, after precise focusing and wavelength separation, reaches the cooled detector 210. The cooled detector 210 operates in a low-temperature environment to reduce thermal noise and improve detection sensitivity. It can convert the received infrared radiation into electrical signals, thereby generating an image. During the operation of the cooled detector 210, the internal components of the cooled detector 210 are protected from damage by the external environment through the detector protection window 212; the background radiation interference is suppressed through the cold screen 214; the field of view of the detector is limited through the cold aperture 216; and the focal plane 218 is responsible for converting the received infrared radiation into electrical signals.

[0017] Table 1 shows the optical structure parameters of the present invention: Table 1

[0018] The aspherical surfaces mentioned in the above eight lenses are all even-order aspherical surfaces, and their expressions are as follows:

[0019] in For an aspherical surface along the optical axis at a height of When the position is such that the distance from the vertex of the non-spherical surface is the sag, Represents the curvature at the vertices of the surface. The conic coefficient, , , , , It represents the higher-order aspheric coefficient.

[0020] Table 2 shows the aspherical coefficients of surfaces S4, S9, S13, and S16: Table 2

[0021] The diffraction surfaces mentioned in the seven lenses above are expressed as follows:

[0022] Where M is the diffraction order. The phase of the diffraction plane. , It is the planned radius of the diffraction surface. , The phase coefficient of the diffraction surface; Table 2 shows the diffraction coefficients of surface S4. Table 2

[0023] The effects of the present invention will be described in further detail below with reference to the aberration analysis diagram.

[0024] Figures 2-4 yes Figure 1 Aberration analysis diagrams of a specific embodiment of the described medium-to-long-wavelength cooled harmonic diffraction lens in the 3.7-4.8μm band. Figure 2 It is an MTF chart. Figure 3 It is a dot-matrix diagram. Figure 4 It is a field distortion diagram; As can be seen from the figure, various aberrations have been well corrected, the diffuse spots have been corrected to near the size of the Alliban, the MTF is close to the diffraction limit, and the distortion does not exceed 0.5%.

[0025] Figures 5-7 yes Figure 1 Aberration analysis diagrams of a specific embodiment of the described medium-to-long-wavelength cooled harmonic diffraction lens in the 7.7-9.6μm band. Figure 2 It is an MTF chart. Figure 3 It is a dot-matrix diagram. Figure 4 It is a field distortion diagram; As can be seen from the figure, various aberrations have been well corrected, the diffuse spots have been corrected to near the size of the Alliban, the MTF is close to the diffraction limit, and the distortion does not exceed 0.5%.

[0026] Therefore, it can be seen that the long-wave cooled dual-band lens in this invention has good imaging quality.

[0027] Through the above steps, by setting up a first lens 110, a second lens 120, a third lens 130, and a cooled detector 210, wherein the cooled detector 210 consists of a window, a cold screen 214, a cold aperture 216, and an imaging focal plane 218, and setting them sequentially from the object side to the image side, a mid-to-long-wave cooled dual-band harmonic diffraction lens with a resolution of 640x512 and a pixel size of 15 micrometers can be formed. The total length of the optical system is 138.42 mm, and the maximum aperture is 96 mm. The imaging quality in both bands is good, and the structure is compact. It can utilize the special dispersion principle of harmonic diffraction optical elements to produce different diffraction effects at different wavelengths, thereby achieving precise control of light in different bands. This can reduce aberrations and effectively correct aberrations over a wide band, solving the problem that existing mid-to-long-wave cooled dual-band detectors, when simultaneously capturing mid-wave and long-wave infrared information, are prone to image quality being affected due to the wide band range, and it is difficult to improve the imaging quality of both bands simultaneously through a single correction method.

[0028] Finally, it should be noted that the above embodiments are only used to illustrate the present invention and are not intended to limit the technical solutions described herein. Therefore, although this specification has described the present invention in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the present invention; and all technical solutions and improvements that do not depart from the spirit and scope of the present invention should be covered within the scope of the claims of the present invention.

Claims

1. A medium-to-long-wavelength cooled dual-band harmonic diffraction lens, comprising a first lens (110); characterized in that: It also includes a second lens (120), a third lens (130), and a cooled detector (210). The second lens (120), the third lens (130), and the cooled detector (210) are arranged sequentially from the object side to the image side along the optical axis. The cooled detector (210) includes a detector protection window (212), a cold screen (214), a cold aperture (216), and a focal plane (218). The cooled detector (210) is encapsulated within the detector protection window (212), and the cold screen (214) is located at the focal plane. The cold detector (210) is located at the front of the photosensitive end, the cold aperture (216) is located in front of the cold screen (214), and the focal plane (218) is located at the rear end of the entire optical system and is close to the cold screen (214) and the cold aperture (216). The first lens (110) is a meniscus silicon positive lens with the convex surface facing the object side and has an aspherical surface on it. The second lens (120) is a biconcave germanium negative lens with a resonant diffraction surface on it. The third lens (130) is a meniscus silicon positive lens with the convex surface facing the object side and has an aspherical surface on it.

2. The medium-to-long-wavelength cooled dual-band harmonic diffraction lens according to claim 1, characterized in that: The lens meets the following parameters: effective focal length EFL = 100mm, F number = 2.0, total optical system length = 138.42mm, compatible detector 640x512, pixel size 15μm.

3. The medium-to-long-wavelength cooled dual-band harmonic diffraction lens according to claim 1, characterized in that: The horizontal field of view of the lens is 2ω = 5.5°.

4. The medium-to-long-wavelength cooled dual-band harmonic diffraction lens according to claim 1, characterized in that: The aspherical surfaces in the lens element satisfy the following expression: ； Where z is the distance vector from the vertex of the aspherical surface at a height of r along the optical axis, c represents the vertex curvature of the surface, k is the conic coefficient, and α2, α3, α4, α5, and α6 are higher-order aspherical coefficients.

5. A medium-to-long-wavelength cooled dual-band harmonic diffraction lens according to claim 1, characterized in that: The diffraction surface in the lens element satisfies the following expression: Ф=M(A1ρ) 2 +A2ρ 4 ), where M is the diffraction order and Ф is the phase of the diffraction plane. , A1 and A2 are the planned radius of the diffraction surface and the phase coefficients of the diffraction surface.

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