A minimalist infrared imager based on planar diffractive lens and image processing method

Abstract

This application provides a simplified infrared imager and image processing method based on a planar diffractive lens, including a planar diffractive imaging optical lens comprising a first lens and a second lens; a detector core assembly including a cooled mid-wave infrared detector, which is an area array detector with a pixel size of 320×256; the detector core assembly having a preprocessing circuit board with an information processing unit; the detector core assembly being detachably connected to the planar diffractive imaging optical lens; the information processing unit being used to recover the image captured by the simplified infrared imager with the planar diffractive lens; by using a planar diffractive lens, this application can reduce the overall weight of the optical system by 60% and the cost by 50% while ensuring imaging quality, meeting the design requirements of miniaturization, lightweighting, and low cost, and ensuring that the overall efficiency of the optical system is greater than 80%.

Description

Technical Field

[0001] This application relates to the field of computational imaging technology, and in particular to a minimalist infrared imager and image processing method based on a planar diffraction lens. Background Technology

[0002] With the rapid development of optoelectronic equipment in military reconnaissance, unmanned vehicles, security monitoring, and disaster relief, the demand for high-quality images is increasing. Currently, optical systems mainly improve imaging quality by increasing the number of lenses or using special surface shapes, but this increases the overall weight of the system, contradicting the requirement for lightweight design. Summary of the Invention

[0003] The purpose of this application is to address the above problems by providing a minimalist infrared imager and image processing method based on a planar diffraction lens.

[0004] First aspect:

[0005] This application provides a minimalist infrared imager based on a planar diffraction lens, comprising:

[0006] A planar diffraction imaging optical lens, comprising a first lens and a second lens;

[0007] The detector core assembly includes a cooled mid-wave infrared detector, which is an area array detector with a pixel size of 320×256; the detector core assembly has a preprocessing circuit board with an information processing unit; the detector core assembly is detachably connected to the planar diffraction imaging optical lens.

[0008] The information processing unit is used to restore a low-resolution image captured by a minimalist infrared imager equipped with the planar diffraction lens to a high-resolution image.

[0009] According to the technical solution provided in the embodiments of this application, the first lens includes a first surface and a second surface, the first surface being a diffraction surface of a planar substrate, and the second surface being an optical plane.

[0010] According to the technical solution provided in the embodiments of this application, the diffraction order of the first surface is +3, and the phase coefficient is C1 = -4.217014 × 10⁻⁶. -3 C2 = 5.308595 × 10 -7 C3 = -1.506733 × 10 -10 C4 = 6.830384 × 10 -14The characteristic wavelength is λ0 = 4200nm, the light transmission aperture range is φ26mm~φ27mm, the light transmission aperture range of the second surface is φ26mm~φ27mm, and the thickness range is 3.4mm~3.6mm.

[0011] According to the technical solution provided in the embodiments of this application, the second lens includes a third surface and a fourth surface, both of which are diffraction surfaces of a planar substrate.

[0012] According to the technical solution provided in the embodiments of this application, the diffraction order of the first surface is +3, and the phase coefficient is C1 = -3.250605 × 10⁻³. -3 C2 = -4.175416 × 10 -6 C3 = 2.541837 × 10 -9 C4 = -8.867419 × 10 -14 The characteristic wavelength is λ0 = 4200 nm, and the aperture range is φ34 mm to φ35 mm; the diffraction order of the second surface is +3, and the phase coefficient is C1 = -6.497982 × 10⁻⁶. -3 C2 = 6.795195 × 10 -6 C3 = -3.402993 × 10 -9 C4 = 2.266358 × 10 -14 The characteristic wavelength is λ0 = 4200nm, the aperture range is φ33mm~φ35mm, and the thickness range is 3.5mm~4.5mm.

[0013] According to the technical solution provided in the embodiments of this application, the optical materials of both the first lens and the second lens are germanium.

[0014] According to the technical solution provided in the embodiments of this application, the distance between the first lens and the second lens varies from 66mm to 67mm.

[0015] The second aspect:

[0016] This application provides a minimalist infrared imager and image processing method based on a planar diffraction lens, the method comprising the following steps:

[0017] A scene is photographed using a minimalist infrared imager based on a planar diffraction lens to form a raw image, which is a low-resolution image.

[0018] The original image and the PSF of the planar diffraction imaging optical lens are input into the information processing unit, which has the ADMM algorithm built in.

[0019] The original image is restored using the ADMM algorithm and the PSF.

[0020] Compared with the prior art, the beneficial effects of this application are as follows: This application connects a planar diffraction imaging optical lens to a detector core assembly, which also has a preprocessing circuit board and an information processing unit. The information processing unit is used to restore the low-resolution original image captured by the minimalist infrared imager based on the planar diffraction lens to a high-resolution image. In use, the minimalist infrared imager based on the planar diffraction lens is used to capture external scenes, and the captured image is input to the information processing unit for processing. The spatial resolution of the processed and restored image can reach the cutoff frequency of the infrared detector. By using a planar diffraction lens, this application can reduce the overall weight of the optical system by 60% and the cost by 50% while ensuring imaging quality. This meets the design requirements of miniaturization, lightweighting, and low cost, and can ensure that the overall efficiency of the optical system is greater than 80%. Attached Figure Description

[0021] Figure 1 A system diagram of a minimalist infrared imager based on a planar diffraction lens is provided for embodiments of this application;

[0022] Figure 2 This is a graph showing the optical transfer function values ​​of a minimalist infrared imager based on a planar diffraction lens.

[0023] Figure 3 This is a flowchart of the image processing of a minimalist infrared imager based on a planar diffraction lens.

[0024] The text labels in the image represent:

[0025] 1. Planar diffraction imaging optical lens; 2. Detector core assembly; 3. Information processing unit. Detailed Implementation

[0026] To enable those skilled in the art to better understand the technical solution of this application, the application will be described in detail below with reference to the accompanying drawings. The description in this section is only exemplary and explanatory, and should not be used to limit the scope of protection of this application in any way.

[0027] Example 1:

[0028] This application provides a minimalist infrared imager based on a planar diffraction lens, with a working wavelength range of 3.5μm to 5.0μm; a field of view of 12° (pitch) × 9.6° (head); a focal length of f = 54mm; and an F-number of 2.0.

[0029] Please refer to Figures 1-3This embodiment provides a minimalist infrared imager based on a planar diffraction lens, comprising:

[0030] A planar diffraction imaging optical lens 1, wherein the planar diffraction imaging optical lens 1 includes a first lens and a second lens;

[0031] The detector core assembly 2 includes a cooled mid-wave infrared detector, which is an area array detector with a pixel size of 320×256; the detector core assembly 2 has a preprocessing circuit board, on which an information processing unit 3 is provided; the detector core assembly 3 is detachably connected to the planar diffraction imaging optical lens 1.

[0032] The information processing unit 3 is used to restore a low-resolution image captured by a minimalist infrared imager equipped with the planar diffraction lens to a high-resolution image.

[0033] Specifically, in this embodiment, according to the optical path direction, from left to right, the first lens and the second lens are arranged in sequence, and the first lens and the second lens are connected and fixed by an optical lens barrel; the detector core assembly 2 includes a cooled mid-wave infrared detector, which is an area array detector with a pixel size of 320×256 and a single pixel size of 30μm; the detector core assembly 2 also includes a preprocessing circuit board, on which an information processing unit 3 is provided. The information processing unit 3 is used to restore the low-resolution original image captured by the minimalist infrared imager based on the planar diffraction lens to a high-resolution image. The detector core assembly 2 and the planar diffraction imaging optical lens 1 are fixed together by screws.

[0034] Furthermore, the first lens includes a first surface and a second surface, the first surface being a diffraction surface of a planar substrate, and the second surface being an optical plane.

[0035] Furthermore, the diffraction order of the first surface is +3, and the phase coefficient is C1 = -4.217014 × 10⁻³. -3 C2 = 5.308595 × 10 -7 C3 = -1.506733 × 10 -10 C4 = 6.830384 × 10 -14 The characteristic wavelength is λ0 = 4200nm, the light transmission aperture range is φ26mm~φ27mm, the light transmission aperture range of the second surface is φ26mm~φ27mm, and the thickness range is 3.4mm~3.6mm.

[0036] Specifically, in this embodiment, the light-transmitting aperture of the first surface ranges from φ26mm to φ27mm; the light-transmitting aperture of the second surface ranges from φ26mm to φ27mm; and the center thickness of the first surface and the second surface ranges from 3.4mm to 3.6mm.

[0037] Furthermore, the second lens includes a third surface and a fourth surface, both of which are diffraction surfaces of a planar substrate.

[0038] Furthermore, the diffraction order of the first surface is +3, and the phase coefficient is C1 = -3.250605 × 10⁻³. -3 C2 = -4.175416 × 10 -6 C3 = 2.541837 × 10 -9 C4 = -8.867419 × 10 -14 The characteristic wavelength is λ0 = 4200 nm, and the aperture range is φ34 mm to φ35 mm; the diffraction order of the second surface is +3, and the phase coefficient is C1 = -6.497982 × 10⁻⁶. -3 C2 = 6.795195 × 10 -6 C3 = -3.402993 × 10 -9 C4 = 2.266358 × 10 -14 The characteristic wavelength is λ0 = 4200nm, the aperture range is φ33mm~φ35mm, and the thickness range is 3.5mm~4.5mm.

[0039] Specifically, in this embodiment, the center thickness of the first surface and the second surface ranges from 3.5 mm to 4.5 mm.

[0040] Furthermore, both the first lens and the second lens are made of germanium.

[0041] Specifically, in this embodiment, both the first lens and the second lens use germanium as the optical material. Germanium is chosen as the optical material because it has a high refractive index and good light transmission performance in the infrared band. In this embodiment, the single-lens optical design is achieved by matching the refractive index of the material with the lens thickness and lens surface shape.

[0042] Furthermore, the distance between the first lens and the second lens varies from 66mm to 67mm;

[0043] Specifically, in this embodiment, the air gap between the first lens and the second lens varies between 66mm and 67mm.

[0044] Example 2:

[0045] This application provides a minimalist infrared imager and image processing method based on a planar diffraction lens, the method comprising the following steps:

[0046] 1. A scene is photographed using a minimalist infrared imager based on a planar diffraction lens to form a raw image, wherein the raw image is a low-resolution image;

[0047] The infrared imager in this embodiment is used to take pictures of the external scene to obtain the original image. The original image is a low-resolution image, which means that the image is a blurry image that is not clear.

[0048] 2. Input the original image and the PSF of the planar diffraction imaging optical lens into the information processing unit, which has a built-in ADMM algorithm;

[0049] Specifically, the original image obtained by shooting and the PSF of the planar diffraction imaging optical lens are input into the information processing unit for processing; the information processing unit has a built-in ADMM algorithm, which is existing technology, and the PSF is a point spread function, which is well known to those skilled in the art.

[0050] 3. Restore the original image using the ADMM algorithm and the PSF;

[0051] Specifically, the first image is obtained by restoring the low-resolution original image using the ADMM algorithm and the PSF of the planar diffraction imaging optical lens. The ADMM algorithm is the alternating direction multiplier method, and the alternating direction multiplier is a prior art.

[0052] 4. An existing standard mid-wave infrared imager is used to photograph the external scene. The scene is the same as the scene photographed by the infrared imager in this embodiment. The operating conditions of the standard mid-wave infrared imager (operating wavelength set to 3.5μm~5.0μm; field of view of 12° (pitch) × 9.6° (heading); focal length of f=54mm; F ​​number of 2.0) are consistent with the operating conditions of the minimalist infrared imager in this application. The image captured by the standard mid-wave infrared imager is denoted as the second image, which is a high-resolution image.

[0053] 5. Input the first image and the second image into the information processing unit for processing. The information processing unit is equipped with a discrimination program that performs similarity discrimination calculation on the first image and the second image based on the SSIM (structural similarity) evaluation method.

[0054] If the similarity between the two is greater than 95%, the first image is taken as the image output by the minimalist infrared imager based on the planar diffraction lens.

[0055] If the similarity between the two is less than 95%, random perturbation should be added to the ADMM algorithm and the PSF to correct them. This correction method is a correction method in the prior art, which will not be described in detail here. Then, steps 3 and 4 are repeated until the similarity between the first image and the second image is greater than 95%.

[0056] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. The above descriptions are only preferred embodiments of this application. It should be noted that due to the limitations of written expression, while there are objectively infinite specific structures, those skilled in the art can make several improvements, modifications, or changes without departing from the principles of this invention, and can also combine the above technical features in an appropriate manner. These improvements, modifications, changes, or combinations, or the direct application of the inventive concept and technical solution to other situations without modification, should all be considered within the scope of protection of this application.

Claims

1. A minimalist infrared imager based on a planar diffraction lens, characterized in that, include: A planar diffraction imaging optical lens (1), the planar diffraction imaging optical lens (1) includes a first lens and a second lens; The detector core assembly (2) includes a cooled mid-wave infrared detector, which is an array detector with a pixel size of 320×256; the detector core assembly (2) has a preprocessing circuit board, on which an information processing unit (3) is provided; the detector core assembly (2) is detachably connected to the planar diffraction imaging optical lens (1); The information processing unit (3) is used to restore the low-resolution image captured by the minimalist infrared imager equipped with the planar diffraction lens to a high-resolution image; The image processing method of the simplified infrared imager includes the following steps: Step 1: Use a minimalist infrared imager based on a planar diffraction lens to capture images of the scene to form a raw image, which is a low-resolution image; Step 2: Input the original image and the PSF of the planar diffraction imaging optical lens into the information processing unit, which has the ADMM algorithm built in. Step 3: Restore the original image using the ADMM algorithm and the PSF. The first image is obtained by restoring the low-resolution original image using the ADMM algorithm and the PSF of the planar diffraction imaging optical lens. Step 4: Use an existing standard mid-wave infrared imager to photograph the external scene. The scene is the same as the scene photographed by the infrared imager, and the operating conditions of the standard mid-wave infrared imager are the same as those of the minimalist infrared imager. The image captured by the standard mid-wave infrared imager is recorded as the second image, which is a high-resolution image. Step 5: Input the first image and the second image into the information processing unit for processing. The information processing unit is equipped with a discrimination program that performs similarity discrimination calculation on the first image and the second image based on the SSIM evaluation method. If the similarity between the two is greater than 95%, the first image is taken as the image output by the minimalist infrared imager based on the planar diffraction lens. If the similarity between the two is less than 95%, random perturbation is added to the ADMM algorithm and the PSF to correct them, and steps 3 and 4 are repeated until the similarity between the first image and the second image is greater than 95%.

2. The minimalist infrared imager based on a planar diffraction lens according to claim 1, characterized in that, The first lens includes a first surface and a second surface, the first surface being a diffraction surface of a planar substrate, and the second surface being an optical plane.

3. The minimalist infrared imager based on a planar diffraction lens according to claim 2, characterized in that, The diffraction order of the first surface is +3, the phase coefficient is C1=-4.217014x10 -3 , C2=5.308595x10 -7 , C3=-1.506733x10 -10 , C4=6.830384x10 -14 , the characteristic wavelength is λ0=4200nm, the range of the clear aperture is φ26mm-φ27mm, the range of the clear aperture of the second surface is φ26mm-φ27mm, and the thickness range is 3.4mm-3.6mm.

4. The minimalist infrared imager based on a planar diffraction lens according to claim 1, characterized in that, The second lens includes a third surface and a fourth surface, both of which are diffraction surfaces of a planar substrate.

5. The minimalist infrared imager based on a planar diffraction lens according to claim 4, characterized in that, The diffraction order of the third surface is +3, and the phase coefficients are C1 = -3.250605 × 10⁻³ and C2 = -4.175416 × 10⁻³. -6 C3 = 2.541837 × 10 -9 C4 = -8.867419 × 10 -14 The characteristic wavelength is λ0 = 4200 nm, and the aperture range is φ34 mm to φ35 mm; the diffraction order of the fourth surface is +3, and the phase coefficient is C1 = -6.497982 × 10⁻⁶. -3 C2 = 6.795195 × 10 -6 C3 = -3.402993 × 10 -9 C4 = 2.266358 × 10 -14 The characteristic wavelength is λ0 = 4200nm, the aperture range is φ33mm~φ35mm, and the thickness range is 3.5mm~4.5mm.

6. The minimalist infrared imager based on a planar diffraction lens according to claim 1, characterized in that, Both the first lens and the second lens are made of germanium.

7. The minimalist infrared imager based on a planar diffraction lens according to claim 1, characterized in that, The distance between the first lens and the second lens varies from 66mm to 67mm.

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