CN220084172U - Snapshot multispectral imaging device based on diffraction lens - Google Patents
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- CN220084172U CN220084172U CN202321683767.XU CN202321683767U CN220084172U CN 220084172 U CN220084172 U CN 220084172U CN 202321683767 U CN202321683767 U CN 202321683767U CN 220084172 U CN220084172 U CN 220084172U
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Abstract
The utility model discloses a snapshot type multispectral imaging device based on a diffraction lens, which comprises an optical system and a spectrum reconstruction module; the optical system is of a common optical axis structure and sequentially comprises a front relay objective, a coded aperture, a diffraction lens and a gray scale area array detector along the direction of an optical path; the back focal plane of the front relay objective lens is overlapped with the front focal plane of the diffraction lens, the coding aperture is arranged on the overlapped focal planes, and the gray area array detector is arranged on the back focal plane of the diffraction lens; and the gray scale area array detector receives the modulated image and obtains a multispectral image after being processed by the spectrum reconstruction module. The snapshot type multispectral imaging device provided by the utility model has a compact structure, can obtain multispectral images of targets by one exposure, has strong instantaneity, and is suitable for dynamic or transient target scenes.
Description
Technical Field
The utility model relates to the technical field of spectral imaging, in particular to a snapshot type spectral imaging device based on a coded aperture and a diffraction lens.
Background
Compared with the traditional two-dimensional imaging technology, the spectrum imaging technology can not only obtain the space information of the target scene, but also obtain the spectrum information of the target. According to the target image and the spectrum characteristics, the information of the components, the distribution, the content and the like of the object can be obtained through analysis, and the intrinsic characteristics of the target object can be more comprehensively known by using the information, so that the spectrum imaging technology is widely applied to scientific research and engineering application, and has wide application and development prospects in the fields of military reconnaissance, remote sensing observation, biomedicine, agricultural environment monitoring, mineral exploration and the like. The spectrum imaging technology is divided into a non-snapshot type spectrum imaging device and a snapshot type spectrum imaging device, wherein the non-snapshot type spectrum imaging device is represented by a line scanning type spectrum imaging spectrometer and a push scanning type spectrum imaging device, most of the non-snapshot type spectrum imaging devices are complex in structure and high in cost, are not suitable for measuring dynamic scenes, and are difficult to popularize in some application fields. In contrast, snapshot spectral imaging techniques can obtain target space and spectral data within a single integration period of the imaging system, and lower cost is beneficial for rapid popularization. Meanwhile, with the development of computational optics, the diffraction optical elements (Diffractive optical elements, DOE) have been successfully applied to diffraction spectrum imaging by virtue of their compact physical dimensions and high design freedom, further reducing the size of the spectrum imaging device and the hardware cost.
Taking a classical coded aperture snapshot spectral imaging camera (Coded Aperture Snapshot Spectral Imager, CASSI) as an example, the structure comprises a dispersive optical element (prism or diffraction grating), a coded aperture, a series of relay lenses, an objective lens, and other imaging lenses. In operation, the dispersive optical element is coupled to the coded aperture via a relay lens to code modulate spectral or spatial spectral characteristics, and then process the compressed data for spectral reconstruction. However, since this method requires the use of a plurality of optical elements to collimate and disperse light, the device structure is complicated, and is limited in many application fields.
Disclosure of Invention
Aiming at the defects of the prior art, the utility model provides a snapshot type multispectral imaging device for obtaining a plurality of wave band spectrum images in a single integration period, and the device structure is simpler and more compact while high-resolution spectrum images are obtained efficiently.
In order to achieve the above object, the present utility model provides a snapshot type multispectral imaging device based on a diffraction lens, which comprises an optical system and a spectrum reconstruction module; the optical system is of a common optical axis structure and sequentially comprises a front relay objective, a coded aperture, a diffraction lens and a gray scale area array detector along the direction of an optical path; the back focal plane of the front relay objective lens is overlapped with the front focal plane of the diffraction lens, the coded aperture is arranged on the overlapped focal plane, and the gray area array detector is arranged on the back focal plane of the diffraction lens; the gray scale area array detector receives the modulated image and obtains a multispectral image after being processed by the spectrum reconstruction module.
The utility model relates to a snapshot multispectral imaging device based on a diffraction lens, wherein a front relay objective lens in an optical system of the device comprises a single objective lens or an imaging lens group for imaging a target scene once; the coding aperture is a transmission coding mask plate with coding distributed randomly; the diffraction lens is a multi-stage Fresnel diffraction lens structure; the gray scale area array detector is a charge coupled device using complementary metal oxide semiconductor materials.
The utility model relates to a snapshot type multispectral imaging device based on a diffraction lens, wherein a spectrum reconstruction module of the device comprises a spectrum image reconstruction unit and an image enhancement unit.
The microstructure height at the radial coordinate r of the structure of the diffraction lens is:wherein M is the number of phase function stages, N 2i Is the coefficient of the item of the 2i degree, [. Cndot.] 2π Representing compression of the phase interval to [0,2 pi ]]Between them; the maximum microstructure height of the diffraction lens is +.>Wherein lambda is the central wavelength, n λ Is the refractive index of the lens material at wavelength lambda.
Compared with the prior art, the utility model has the characteristics and advantages that: the coded aperture and a single diffraction lens are adopted to replace a prism group in a traditional device to realize imaging and dispersion, so that the device is light and miniaturized, a multispectral image of a target can be obtained through one exposure, and the device is suitable for dynamic or transient target scenes.
Drawings
Fig. 1 is a schematic structural diagram of a snapshot-type multispectral imaging device based on a diffraction lens according to an embodiment of the present utility model;
wherein: 1. the system comprises a front relay objective lens, a coded aperture, a diffraction lens, a gray scale area array detector and a spectrum reconstruction module.
Fig. 2 is a schematic structural diagram of a diffraction lens of a snapshot-type multispectral imaging system based on a diffraction lens according to an embodiment of the present utility model.
Detailed Description
The technical scheme of the utility model is further described in detail below with reference to the accompanying drawings and examples.
Referring to fig. 1, a schematic structural diagram of a snapshot multispectral imaging device based on a coded aperture and a diffraction lens provided in this embodiment includes an optical system and a spectrum reconstruction module 5, and in this embodiment, the device includes a front relay objective lens 1, a coded aperture 2, a diffraction lens 3 and a gray-scale area array detector 4 sequentially along a light path direction.
In this embodiment, the front relay objective lens 1 of the optical system is used for imaging the target scene once, and a single objective lens or an imaging lens group can be adopted; the coded aperture 2 is a transmission type coded mask plate, and the coded form is random distribution; the diffraction lens 3 is a multi-stage Fresnel diffraction lens structure; the gray scale area array detector is a charge coupled device using complementary metal oxide semiconductor materials.
The optical system is of a common optical axis structure, the back focal plane of the front relay objective lens 1 is overlapped with the front focal plane of the diffraction lens 3, the code aperture 2 is arranged on the overlapped focal plane, and the gray scale area array detector 4 is arranged on the back focal plane of the diffraction lens; the gray scale area array detector inputs the received modulated image into a spectrum reconstruction module 5, and the multispectral image is obtained after the received modulated image is processed by a spectrum image reconstruction unit and an image enhancement unit of the spectrum reconstruction module.
The snapshot multispectral imaging device based on the coded aperture and the diffraction lens provided by the embodiment has the following imaging working steps and principles:
1. spatial modulation of target scene images converged by a pre-relay objective lens by a coding aperture
The pre-relay objective images the target collimated through the coded aperture of the back focal plane, assuming that the spectral image of the target scene is represented as I 0 (x, y, λ), where x, y represents spatial information of the object and λ represents spectral information of the object scene. After the target passes through the pre-system and the coding aperture, the spectral intensity distribution is as follows:
I 1 ＝I 0 (x,y,λ)·T(x,y)#(1)######
where T (x, y) is the transmittance function of the coded aperture in the form of a random distribution, T (x, y) ε {0,1}.
2. Spectral modulation of a target scene image by a diffractive lens
The incident light reaches the diffraction lens after amplitude modulation of the coded aperture, and the diffraction lens disperses the incident light.
Let the distance d between the point source with wavelength lambda and the diffraction lens through the code aperture propagate to the front surface u of the diffraction lens 1 The incident wavefield at locations x, y may be expressed as:
wave field passing through diffraction lens, introducing phase delay phi (x, y), wave field u 2 Expressed as:
phase retardation phi (x, y) and diffraction lens height h (x, y) and refractive index n of the diffraction lens material at lambda wavelength λ The following are related:
φ(x,y,λ)＝(n λ -1)h(x,y)#(4)##
wherein the microstructure height at radial coordinate r on the diffractive lens is:
wherein M is the number of phase function stages, N 2i Is the coefficient of the item of the 2i degree, [. Cndot.] 2π Representing compression of the phase interval to [0,2 pi ]]In between the two,is the maximum microstructure height of the diffraction lens, and is obtained by taking the refractive index n λ A height of 2 pi phase retardation is generated at wavelength lambda. For convenience of preparation and processing, the diffraction lens microstructure height h (r) is discretized, and the structure is shown in fig. 2, namely, each zone height takes an integer multiple of the maximum microstructure height divided by the quantization level Q:
3. gray area array detector receives image
The light wave field reaches a detector plane with a distance z from the DOE, and the wave field on the gray scale area array detector can be obtained by a Fresnel diffraction formula:
wherein the method comprises the steps ofIs wave number. PSF and wavefield u 3 Is proportional to the square of:
PSF(u,v,λ)∝|u 3 u,v)| 2 #(8)#
after the PSF is determined, the image at the post-DOE distance z can be expressed as a convolution of the image through the coded aperture with the PSF:
the gray scale area array detector receives the superposition of the blurred image after the spectrum is modulated, and solves the inverse problem that the spectrum definition spectrum image is ill-conditioned from the blurred image, and can be expressed as the following formula (10):
where J represents the spectral aliased image, I represents the reconstructed spectral data cube, Φ represents the degradation function of the system,represents the value of x when f (x) takes the minimum value, < + >>Representing the square of the two norms ρ q R q (T) is a regularization term, regularization function R q (T) specific properties in the code aperture and the diffractive lens can be enhanced, aiming to ensure that the code satisfies specific realizability, transitivity, correlation between snapshots and conditional constraints, ρ q Is a regularization parameter.
4. Spectral reconstruction
And obtaining a multispectral image after the spectrum image reconstruction and the image enhancement processing.
The snapshot multispectral imaging device provided by the embodiment can reconstruct high-quality multispectral images of 28 channels in total of 430-700 nm, the average Peak signal-to-noise ratio (PSNR) of the reconstruction result of the test set spectral images is 34.12, the average structural similarity (Structural Similarity, SSIM) is 0.94, and the average spectral angle matching (spectral angle mapping, SAM) is 0.058.
Claims (7)
1. Snapshot multispectral imaging device based on diffraction lens, including optical system and spectrum reconstruction module (5), its characterized in that: the optical system is of a common optical axis structure and sequentially comprises a front relay objective lens (1), a coded aperture (2), a diffraction lens (3) and a gray scale area array detector (4) along the direction of an optical path; the back focal plane of the front relay objective lens is overlapped with the front focal plane of the diffraction lens, the coded aperture is arranged on the overlapped focal plane, and the gray area array detector is arranged on the back focal plane of the diffraction lens; the gray scale area array detector receives the modulated image and obtains a multispectral image after being processed by the spectrum reconstruction module.
2. A snapshot multispectral imaging device based on a diffraction lens according to claim 1, characterized in that the pre-relay objective (1) comprises a single objective or imaging lens group that images the target scene once.
3. The diffraction-lens-based snapshot multispectral imaging device according to claim 1, wherein the coded apertures (2) are transmissive coded masks with randomly distributed codes.
4. The diffraction-lens-based snapshot multispectral imaging device according to claim 1, wherein the diffraction lens (3) is a multi-stage fresnel diffraction lens structure.
5. The diffraction-lens-based snapshot multispectral imaging device of claim 1, wherein the gray-scale area array detector is a charge-coupled device using complementary metal oxide semiconductor materials.
6. The diffraction lens-based snapshot multispectral imaging device of claim 1, wherein the spectrum reconstruction module comprises a spectrum image reconstruction unit and an image enhancement unit.
7. A diffraction lens-based snapshot multispectral imaging device according to claim 1 or 4, wherein: the microstructure height at the radial coordinate r of the diffraction lens (3) is as follows: wherein M is the number of phase function stages, N 2i Is the coefficient of the item of the 2i degree, [. Cndot.] 2π Representing compression of the phase interval to [0,2 pi ]]Between them; the maximum microstructure height of the diffraction lens is +.>Wherein lambda is the central wavelength, n λ Is the refractive index of the lens material at wavelength lambda.
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