Built-in imaging system and method based on rotary scanning polarization filtering module

Abstract

The invention relates to a built-in imaging system and method based on a rotary scanning polarization filtering module, the system comprises a front imaging lens group, the rotary scanning polarization filtering module, a rear imaging lens group, an imaging detector and an upper computer, the rotary scanning polarization filtering module comprises a polarization filtering chip, compressing the target radiation light beam through a front imaging lens group and converging the target radiation light beam into parallel light; the parallel light enters a rotary scanning polarization filtering module, the rotary scanning polarization filtering module is modulated to different direction angles through an upper computer, and polarized light in different vibration directions is obtained through polarization of a polarization filtering chip; polarized light in different vibration directions is focused on an imaging detector through a rear imaging lens group for imaging, and a polarized image is obtained. Compared with the prior art, the compact system design is realized, the polarization information acquisition capability of different application scenes is met, and the application range of polarization imaging in the fields of target detection and identification and the like is expanded.

Description

Technical Field

[0001] The present invention relates to the technical field of polarization imaging, and in particular to a built-in imaging system and method based on a rotating scanning polarization filter module. Background Art

[0002] Polarimetric Imaging (PI) is a multidisciplinary and cutting-edge photoelectric detection technology that organically combines intensity imaging and polarization characteristics. By acquiring rich multi-dimensional and refined characteristic information of the target, it can distinguish the polarization characteristic differences of the surface properties of the material (roughness, water content, material properties, etc.). It has the application advantages of suppressing the natural background and highlighting the artificial target. It has broad application prospects in the fields of detection remote sensing, target recognition, biomedicine and materials science. The polarization imaging system is the key to target information acquisition and feature deconstruction. It achieves the purpose of deconstructing polarization characteristics by collecting three or more polarization information images at different directions and angles and combining them with processing algorithms. According to the principle of the spectroscopic element and the collection method of polarization information, the polarization imaging system can be divided into four categories: time-sharing type, amplitude-sharing type, aperture-sharing type and focal plane-sharing type. Among them, the amplitude-sharing polarization imaging system has a complex structure and high requirements for optical path registration. In addition, due to the use of multiple detectors and sub-optical path architecture, it has the disadvantages of high manufacturing cost and large volume, which makes it difficult to meet the development needs of compactness and lightweight. The aperture-type polarization imaging system sacrifices spatial resolution in exchange for temporal resolution. Although it achieves real-time imaging of dynamic / static targets, it has shortcomings such as low spatial resolution, loss of image details and poor imaging quality, making it difficult to meet the requirements of high-quality and delicate imaging detection. The focal plane-type polarization imaging system based on micro-nano polarization arrays achieves pixel-level integration of polarization devices and imaging detectors, but is limited by the fixed arrangement of polarization devices. The system can only obtain information on four different polarization directions of the target and the multiple sub-channel structure will still cause a lack of spatial resolution, making it difficult to accurately reconstruct the polarization characteristics of the scene.

[0003] At present, the time-sharing polarization imaging system usually adopts the method of rotating polarization optical devices to obtain polarization information images at different directions and angles in discrete time series. It has the advantages of simple structure, convenient tuning, high imaging resolution, etc., and can overcome the shortcomings of low efficiency and poor real-time performance of traditional systems through ultra-high-speed and high-positioning precision rotating wheels, and is expected to meet the application requirements of real-time imaging detection of targets under complex backgrounds. For example, the intensity-time integration type fast polarization imaging method and device disclosed in patent application CN114216562A directly places the polarization optical element in front of the high-speed imaging module and lens for imaging, which improves the real-time problem of the traditional time-sharing method. However, this system architecture is difficult to realize the application of large focal length and long-distance imaging lenses under the constraint of the limited aperture of the polarization optical element, and the system volume is large, which is difficult to apply to unmanned platforms with limited load space. For example, a fast polarization imaging device and method based on the time-sharing method proposed in patent application CN113055566A places the polarization optical element between the camera module and the optical imaging lens, so that the external light converges and passes through the polarization optical element before being incident on the camera target surface. This method solves the problems of small field of view and limited use of large focal length lenses in existing polarization imaging systems. However, the converged light incident on the polarization optical element introduces non-uniform polarization modulation into the system, resulting in significant detection errors. In addition, the use of traditional rotational drive structure and discrete combination architecture still means that the system still has the problem of low integration.

[0004] The existing system, due to the use of traditional imaging architecture, has problems such as large size, heavy weight, poor integration, and non-uniform polarization modulation, making it difficult to apply to platforms with limited carrying capacity and complex working environments. In addition, due to the use of a front-end system architecture design, the flexible matching of different focal length lenses and the development of functions such as autofocus in the polarization imaging system are often limited, resulting in the system's shortcomings such as short detection distance and poor environmental adaptability. Summary of the invention

[0005] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and to provide a built-in imaging system and method based on a rotating scanning polarization filter module, to achieve a compact, high-performance and customized system design, to meet the polarization information acquisition capabilities of different application scenarios, and to expand the application scope of polarization imaging in target detection and recognition and other fields.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] A built-in imaging system based on a rotating scanning polarization filter module comprises a front imaging lens group, a rotating scanning polarization filter module, a rear imaging lens group, an imaging detector and a host computer, wherein the rotating scanning polarization filter module comprises a polarization filter chip, and the optical axes of the front imaging lens group, the rotating scanning polarization filter module, the rear imaging lens group and the imaging detector coincide with each other, and a target radiation beam is compressed and converged into parallel light through the front imaging lens group; the parallel light enters the rotating scanning polarization filter module, and the rotating scanning polarization filter module is modulated to different direction angles by the host computer, and polarization light with different vibration directions is obtained by polarization using the polarization filter chip; the polarization light with different vibration directions is focused on the imaging detector by the rear imaging lens group for imaging, and a polarized image is obtained.

[0008] Furthermore, the polarization filter chip is obtained by depositing a zinc sulfide-germanium-gold multilayer filter film structure on a substrate, and preparing a micro-nano array structure on the zinc sulfide-germanium-gold multilayer filter film structure.

[0009] Furthermore, the material of the substrate includes multiple materials selected from the group consisting of glass, silicon, zinc sulfide and barium fluoride.

[0010] Furthermore, the front imaging lens group and the rear imaging lens group include multiple types of ultraviolet band lenses, visible light band lenses and infrared band lenses, and the materials of the imaging lens group and the rear imaging lens group match the requirements of the usage scenario and the electromagnetic wave characteristics of the working band.

[0011] Furthermore, the ultraviolet band lens includes multiple materials selected from quartz glass and fluoride crystals, the visible light band lens includes glass, and the infrared band lens includes multiple materials selected from silicon, germanium, zinc sulfide and zinc selenide.

[0012] Furthermore, the imaging detector captures the polarized light with different vibration directions focused by the rear imaging lens group, converts the optical signal of the polarized light into an electrical signal, and generates a polarization image.

[0013] Furthermore, the host computer performs polarization information extraction and target detection on the polarization image.

[0014] Furthermore, the imaging detector includes multiple types of ultraviolet detectors, visible light detectors, near infrared detectors, medium-wave infrared detectors or long-wave infrared detectors.

[0015] Furthermore, the rotation scanning polarization filter module is driven by an electromagnetically driven planar stepping motor, and the rotation angle control and scanning frequency modulation are realized by a driving control signal.

[0016] According to another aspect of the present invention, there is provided a built-in imaging method based on a rotating scanning polarization filter module, comprising the following steps:

[0017] The target radiation beam is compressed and converged into parallel light through the front imaging lens group;

[0018] The parallel light enters the rotating scanning polarization filter module, and the upper computer modulates the rotating scanning polarization filter module to different direction angles, and polarization filter chips are used to polarize to obtain polarized light with different vibration directions;

[0019] The polarized light with different vibration directions is focused onto the imaging detector through a rear imaging lens group for imaging, thereby obtaining a polarized image.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. The present invention forms a built-in imaging system based on a rotating scanning polarization filter module through a front imaging lens group, a rotating scanning polarization filter module, a rear imaging lens group, an imaging detector and a host computer. The rotating scanning polarization filter module is placed in the parallel light path of a specially designed optical system, thereby solving the technical defects of the existing time-sharing polarization imaging system, such as the difficulty in compact integration, the limited use of optical lenses, and the poor flexibility of system design, and realizing compact system design, thereby meeting the polarization information acquisition capabilities of different application scenarios.

[0022] 2. The present invention embeds the polarization filter chip into the optical path of the imaging lens, which reduces the processing requirements of large-aperture polarization filter chips while achieving flexible adaptation and rapid replacement of larger focal length imaging lenses. By modulating the built-in rotating scanning polarization filter module, it is possible to obtain arbitrary polarization state information images of static / dynamic targets in complex scenes without sacrificing spatial resolution, which is beneficial to high-precision detection and identification of targets. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a structural schematic diagram of a built-in imaging system based on a rotating scanning polarization filter module proposed by the present invention;

[0024] Figure 2 It is a structural schematic diagram of a rotation scanning polarization filter module;

[0025] Figure 3 A schematic diagram of a flow chart of a built-in imaging method based on a rotating scanning polarization filter module proposed by the present invention;

[0026] Figure 4 It is a schematic diagram of the structure of the polarization filter chip;

[0027] Figure 5Schematic diagram of TM transmittance of polarization filter chip;

[0028] Figure 6 Schematic diagram of the extinction ratio of the polarization filter chip;

[0029] Figure 7 This is an imaging point diagram of a built-in imaging system based on a rotating scanning polarization filter module;

[0030] Figure 8 This is a modulation transfer function curve of the built-in imaging system based on the rotating scanning polarization filter module.

[0031] Legend: 1. Front imaging lens group; 2. Rotating scanning polarization filter module; 3. Polarization filter chip; 4. Rear imaging lens group; 5. Imaging detector. DETAILED DESCRIPTION

[0032] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0033] Abbreviations involved:

[0034] Root Mean Square, RMS

[0035] Modulation Transfer Function: Modulation Transfer Function, MTF

[0036] TM polarization: Transverse Magnetic, TM

[0037] TE polarization: Transverse Electric, TE

[0038] Noise Equivalent Temperature Difference, NETD

[0039] Example 1

[0040] This embodiment provides a built-in imaging system based on a rotating scanning polarization filter module, such as Figure 1The system shown includes: a front imaging lens group 1, a rotating scanning polarization filter module 2, a rear imaging lens group 4, an imaging detector 5 and a host computer. The rotating scanning polarization filter module 2 includes a polarization filter chip 3. The optical axes of the front imaging lens group 1, the rotating scanning polarization filter module 2, the rear imaging lens group 4 and the imaging detector 5 coincide with each other, and the target radiation beam is compressed and converged into parallel light through the front imaging lens group 1; the parallel light enters the rotating scanning polarization filter module 2, and the rotating scanning polarization filter module 2 is modulated to different directions by the host computer, and polarization filter chip 3 is used to polarize to obtain polarized light with different vibration directions; polarized light with different vibration directions is focused on the imaging detector 5 by the rear imaging lens group 4 for imaging to obtain a polarized image.

[0041] The front imaging lens group 1 and the rear imaging lens group 4 include various types of ultraviolet band lenses, visible light band lenses and infrared band lenses. The materials of the imaging lens group 1 and the rear imaging lens group 4 match the requirements of the usage scenarios and the electromagnetic wave characteristics of the working band. The ultraviolet band lenses include various types of quartz glass and fluoride crystals, the materials of the visible light band lenses include glass, and the materials of the infrared band lenses include various types of silicon, germanium, zinc sulfide and zinc selenide.

[0042] The front imaging lens group 1 is used to compress and modulate the incident light of the scene target into approximately parallel light, eliminate spherical aberration and field curvature within the design band, and prevent polarization information errors caused by excessive incident angles of the light beam through the rotating scanning polarization filter module 2. In addition, according to the requirements of the use scenario and the electromagnetic wave characteristics of the working band, in this embodiment, the front imaging lens group 1 is composed of two infrared band lenses made of germanium material, and the lens transmittance is improved by surface coating.

[0043] like Figure 2 As shown, the rotating scanning polarization filter module 2 includes a polarization filter chip 3. The host computer modulates the rotating scanning polarization filter module 2 to different angles, and uses the polarization filter chip 3 to polarize to obtain polarized light in different vibration directions, thereby obtaining image information under different polarization states. The rotating scanning polarization filter module 2 can be placed in the middle of the front imaging lens group 1 and the rear imaging lens group 4 as a whole, and pins and holes are reserved to facilitate the lead-out of the drive control leads. In addition, according to the rotation drive mode, it is an electromagnetically driven planar stepping motor, and the purpose of rotation angle control and scanning frequency modulation can be achieved through the drive control signal.

[0044] The polarization filter chip 3 is used for modulating the different vibration directions of the incident light field, and its substrate material can be glass, silicon, zinc sulfide, barium fluoride, etc., to achieve the selection of specific spectral bands and different polarization state information. In this embodiment, the polarization filter chip 3 is obtained by depositing a multilayer filter film system structure of zinc sulfide (ZnS)-germanium (Ge)-gold (Au) on a double-throw zone melting high-resistance silicon substrate, and preparing a micro-nano array structure on the multilayer filter film system structure, such as Figure 4 The specific performance parameters of the polarization filter chip 3 are: in the 8-12 μm band, the TM wave peak transmittance is higher than 80%, as shown in FIG. Figure 5 As shown; the half-width of the spectrum is about 1.3μm and the extinction ratio in the band corresponding to the bandwidth is better than 100:1 (20dB), such as Figure 6 shown.

[0045] The rear imaging lens group 4 is used to focus the light beam passing through the polarization filter chip 3. According to the usage scenario requirements and the electromagnetic wave characteristics of the working band, it is composed of three infrared band lenses made of germanium material, and the surface coating is used to improve the lens transmittance.

[0046] The imaging detector 5 is used to convert infrared radiation signals into electrical signals, capture polarized light of different vibration directions focused by the rear imaging lens group 4, and generate digital image data. The working band of the imaging detector 5 includes a variety of ultraviolet detectors, visible light detectors, near-infrared detectors, medium-wave infrared detectors or long-wave infrared detectors according to the requirements of the use scenario. In this embodiment, the imaging detector 5 uses the Gaode Zhigan PLUG617 uncooled infrared detector, which has a pixel number of 640×512, a pixel size of 17μm, a band range of 8 to 14μm, and an imaging equivalent noise temperature difference NETD≤40mK. In addition, the infrared detector uses a USB interface, an operating frequency of 25Hz, and supports 8bit and 14bit digital image output.

[0047] The host computer is responsible for data processing, storage and display, as well as driving and controlling the rotating scanning polarization filter module 2. The host computer is connected to the imaging detector 5, and is used to receive digital image data from the imaging detector 5, and perform image processing and analysis in combination with the back-end algorithm; and is connected to the rotating scanning polarization filter module 2, and is used to drive the rotating scanning polarization filter module 2 to rotate to a specified direction angle.

[0048] Example 2

[0049] This embodiment provides a built-in imaging method based on a rotating scanning polarization filter module, such as Figure 3 As shown, the following steps are included:

[0050] S1. Compress the target radiation beam through the front imaging lens 1 and converge it into parallel light.

[0051] The radiation beam of the scene target enters the front imaging lens group 1, and the target radiation beam is compressed by the front imaging lens group 1 and modulated into approximately parallel light.

[0052] S2, parallel light enters the rotating scanning polarization filter module 2, and the upper computer modulates the rotating scanning polarization filter module 2 to different direction angles, and uses the polarization filter chip 3 to polarize to obtain polarized light with different vibration directions.

[0053] The parallel light of the target radiation beam enters the rotating scanning polarization filter module 2, passes through the polarization filter chip 3, and is polarized by the polarization filter chip 3 to obtain polarized light; the rotating scanning polarization filter module 2 is modulated to different directions and angles by the host computer, so as to obtain polarized light with different vibration directions by using the polarization filter chip 3 to polarize.

[0054] S3. The polarized light with different vibration directions is focused onto the imaging detector 5 through the rear imaging lens 4 to obtain a polarized image.

[0055] After polarized light with different vibration directions enters the rear imaging lens 4, the polarized light is focused onto the imaging detector 5, and imaging is performed by the imaging detector 5 to obtain a polarized image.

[0056] In another preferred embodiment, it also includes:

[0057] S4. Extract polarization information and detect targets from polarization images through a host computer.

[0058] Polarization information is extracted and targets are detected from polarization images using the existing back-end deconstruction algorithm on the host computer.

[0059] The main evaluation criteria for aberration analysis are the spot diagram and the root mean square (RMS) radius diagram. The spot diagram analyzes the phase difference and its cause based on the geometric size and shape of the image point dispersion spot. It can most intuitively determine whether the light spots formed by two adjacent wavelengths are sufficiently separated on the image plane. The RMS diagram reflects the root mean square radius of the light spot in the full band range, and the degree of light spot concentration can be used to show the uniformity of imaging. Figure 7 The figure shows a point diagram of a built-in imaging system based on a rotating scanning polarization filter module in this embodiment. It can be seen that the radius of the Airy disk of the optical system is 17.12 μm, and the point array size of each field of view is smaller than the Airy disk size, which proves that the imaging quality of the optical system is good. Figure 8 The figure shows the MTF curve corresponding to the optical system. It can be seen that the MTF curves of each field of view are close to the diffraction limit and the imaging quality meets the requirements.

[0060] The rest is the same as in Example 1.

[0061] The preferred specific embodiments of the present invention are described in detail above. It should be understood that a person skilled in the art can make many modifications and changes based on the concept of the present invention without creative work. Therefore, any technical solution that can be obtained by a person skilled in the art through logical analysis, reasoning or limited experiments based on the concept of the present invention on the basis of the prior art should be within the scope of protection determined by the claims.

Claims

1. A built-in imaging system based on a rotating scanning polarization filter module, characterized in that: The invention comprises a front imaging lens group (1), a rotating scanning polarization filter module (2), a rear imaging lens group (4), an imaging detector (5) and a host computer. The rotating scanning polarization filter module (2) comprises a polarization filter chip (3). The optical axes of the front imaging lens group (1), the rotating scanning polarization filter module (2), the rear imaging lens group (4) and the imaging detector (5) are mutually coincident. The target radiation beam is compressed and converged into parallel light through the front imaging lens group (1); the parallel light enters the rotating scanning polarization filter module (2), the host computer modulates the rotating scanning polarization filter module (2) to different direction angles, and the polarization filter chip (3) is used to polarize to obtain polarized light with different vibration directions; the polarized light with different vibration directions is focused on the imaging detector (5) by the rear imaging lens group (4) for imaging, and a polarized image is obtained.

2. The built-in imaging system based on the rotating scanning polarization filter module according to claim 1, characterized in that: The polarization filter chip (3) is obtained by depositing a zinc sulfide-germanium-gold multilayer filter film system structure on a substrate, and preparing a micro-nano array structure on the zinc sulfide-germanium-gold multilayer filter film system structure.

3. The built-in imaging system based on the rotating scanning polarization filter module according to claim 2, characterized in that: The material of the substrate includes various ones of glass, silicon, zinc sulfide and barium fluoride.

4. The built-in imaging system based on the rotating scanning polarization filter module according to claim 1, characterized in that: The front imaging lens group (1) and the rear imaging lens group (4) include multiple types of ultraviolet band lenses, visible light band lenses and infrared band lenses, and the materials of the imaging lens group (1) and the rear imaging lens group (4) match the requirements of the use scene and the electromagnetic wave characteristics of the working band.

5. The built-in imaging system based on the rotating scanning polarization filter module according to claim 4, characterized in that: The ultraviolet band lens includes multiple materials of quartz glass and fluoride crystal, the material of the visible light band lens includes glass, and the material of the infrared band lens includes multiple materials of silicon, germanium, zinc sulfide and zinc selenide.

6. The built-in imaging system based on the rotating scanning polarization filter module according to claim 1, characterized in that: The imaging detector (5) captures the polarized light with different vibration directions focused by the rear imaging lens group (4), converts the optical signal of the polarized light into an electrical signal, and generates a polarization image.

7. The built-in imaging system based on the rotating scanning polarization filter module according to claim 1, characterized in that: Polarization information extraction and target detection are performed on the polarization image by the host computer.

8. The built-in imaging system based on the rotating scanning polarization filter module according to claim 1, characterized in that: The imaging detector (5) comprises multiple types of ultraviolet detectors, visible light detectors, near infrared detectors, medium-wave infrared detectors or long-wave infrared detectors.

9. The built-in imaging system based on the rotating scanning polarization filter module according to claim 1, characterized in that: The rotation scanning polarization filter module (2) is driven by an electromagnetically driven planar stepping motor, and rotation angle control and scanning frequency modulation are achieved through a driving control signal.

10. A built-in imaging detection method based on a rotating scanning polarization filter module, characterized in that: The following steps are involved: The target radiation beam is compressed and converged into parallel light through a front imaging lens group (1); The parallel light enters the rotating scanning polarization filter module (2), and the rotating scanning polarization filter module (2) is modulated to different directions and angles by the host computer, and polarization is performed by the polarization filter chip (3) to obtain polarized light with different vibration directions; The polarized light with different vibration directions is focused onto the imaging detector (5) through a rear imaging lens group (4) for imaging, thereby obtaining a polarized image.

Images