Non-uniform microlens array super-resolution plane interference photoelectric imaging system

Abstract

The invention discloses a non-uniform microlens array super-resolution plane interference photoelectric imaging system, and relates to the technical field of super-resolution and interference imaging. A plurality of interference arms arranged in the radial direction are evenly fixed to the substrate in the circumferential direction, a plurality of micro-lenses in the middle layers of the interference arms are arranged in a mirror symmetry mode along the center line, the calibers of the micro-lenses decrease progressively from the two ends to the middle, every two micro-lens pairs in mirror symmetry form an interference base line, and a plurality of micro-tubes on the top layers of the interference arms are consistent with the calibers of the corresponding micro-lenses and are coaxially arranged. The bottom layer of the interference arm is composed of an information processing module and a plurality of coupling interference units, every two microlens pairs are connected with the input end of one coupling interference unit through optical fibers, and the information processing module is connected with the output ends of the coupling interference units through optical fibers. The long interference base line is adopted to obtain the resolution exceeding that of a traditional imaging system, the microlens array with the non-uniform caliber is adopted to enable the long interference base line to obtain the high signal-to-noise ratio so as to enhance the definition of high-frequency details, and the advantages of being short in length, small in size and light in weight are achieved.

Description

Technical Field

[0001] The invention relates to the technical field of super-resolution and interference imaging, in particular to a non-uniform microlens array super-resolution planar interference photoelectric imaging system. Background Art

[0002] Resolution is an important performance indicator for evaluating optoelectronic imaging systems, and it characterizes the degree of refinement of the images acquired by the system. In order to improve the resolution of remote sensing imaging systems, the aperture of the optical system also needs to be continuously increased. The Hubble Space Telescope with an aperture of 2.4m and the Herschel Astronomical Telescope with an aperture of 3.5m are the two largest single-aperture optoelectronic imaging systems currently in orbit, and they are close to the limit of single-aperture processing capabilities.

[0003] In order to achieve a larger optical aperture, the United States has successively proposed imaging schemes such as the spliced ​​reflective primary mirror represented by the James Webb Space Telescope and the spliced ​​thin film transmission primary mirror represented by the MOIRE satellite. Although the aperture of the spliced ​​primary mirror is greatly reduced after folding, the imaging system needs to have a sufficiently large length to obtain the effective focal length for imaging, which leads to a large length, large volume, and heavy weight of the imaging system. Although increasing the aperture can improve the optical resolution of the imaging system, the pixel size of the photodetector limits the room for improving the resolution of the photoelectric imaging system. Limited by the undersampling effect of the photodetector, the cost and technical risk of improving the resolution of the photoelectric imaging system by reducing the pixel size and improving the sampling mode at the hardware process level is very high. Therefore, achieving super-resolution imaging without changing the hardware level of the detector is of great significance to the design and application of the photoelectric imaging system, and is at the forefront of the design and application research field of the photoelectric imaging system.

[0004] Interferometric imaging technology initially used small-aperture telescopes that were several to hundreds of meters apart to collect light. A pair of telescopes formed an interference baseline, which was changed by moving the telescopes to obtain more sampling spectra. Although this technology can achieve extremely high resolution, the entire imaging system is bulky, and it takes hours to days to complete an imaging session. The Segmented Planar Imaging Detector for Electro-optical Reconnaissance (SPIDER) uses a microlens array to collect light, implements interference pairing, phase adjustment, waveguide coupling, and coherent detection in photonic integrated circuits, and obtains spatial images through signal processing. It can reduce the length and weight of the optical system by 10 to 100 times, but SPIDER has not yet achieved a resolution higher than that of traditional optoelectronic imaging systems.

[0005] In order to achieve super-resolution imaging, scholars at home and abroad have carried out research on methods such as random optical reconstruction microscopy, structured illumination microscopy, stacked imaging, and superlens imaging. However, these imaging methods have only achieved super-resolution imaging in the microscopic field, and no progress has been made in the conventional macroscopic large-scale imaging field. Summary of the invention

[0006] In order to solve the shortcomings of the background technology, the present invention provides a non-uniform microlens array super-resolution planar interference photoelectric imaging system, which adopts a long interference baseline to obtain a resolution that exceeds that of traditional imaging systems. A non-uniform aperture microlens array is used to enable the long interference baseline to obtain a high signal-to-noise ratio to enhance the clarity of high-frequency details. It has the advantages of short length, small size and light weight.

[0007] To achieve the above-mentioned purpose, the present invention adopts the following technical scheme: a non-uniform microlens array super-resolution planar interference photoelectric imaging system, comprising a substrate and a plurality of interference arms, wherein the plurality of interference arms are uniformly fixed in an annular direction on the surface of the substrate, and the plurality of interference arms are arranged radially, the middle layer of each interference arm is composed of a plurality of microlenses of an even number, the plurality of microlenses are arranged mirror-symmetrically along the center line and the aperture is set decreasingly from both ends to the middle, each of the two mirror-symmetrical microlenses is paired and forms an interference baseline, the top layer of each interference arm is composed of a plurality of microtubes, the plurality of microtubes are consistent with the aperture of the corresponding microlens and are coaxially arranged, the bottom layer of each interference arm is composed of an information processing module and a plurality of coupling interference units, each pair of two microlenses is connected to an input end of a coupling interference unit through an optical fiber, and the information processing module is connected to the output ends of the plurality of coupling interference units through an optical fiber.

[0008] Furthermore, the super-resolution imaging conditions of the imaging system are:

[0009]

[0010] In the formula, B max is the length of the longest interference baseline, f is the focal length of the diffraction limited optoelectronic imaging system, λ is the central wavelength of the imaging band, and a is the side length of the detector pixel of the diffraction limited optoelectronic imaging system.

[0011] Furthermore, the two microlenses on the interference baseline transmit the optical signal to the corresponding coupling interference unit through the optical fiber at the rear focus for spectral splitting and coherent superposition to form interference fringes. After the information processing modules of all the interference arms convert the interference fringes output by the corresponding multiple coupling interference units into electrical signals, the electrical signals are uniformly inverse Fourier transformed to obtain the imaging image.

[0012] Furthermore, let the visibility of the interference fringes be V, and the component of the interference baseline in the x-axis direction be B x, plot V and B x The relationship curve of the interference fringe visibility is shown in FIG. 1 , and the aperture values ​​of the multiple microlenses on the interference arm increase according to the square root value of the inverse of the interference fringe visibility in the relationship curve as the interference baseline length increases.

[0013] Compared with the prior art, the beneficial effects of the present invention are: the present invention adopts a long baseline to obtain a higher resolution than the traditional optoelectronic imaging system, and adopts a microlens array with non-uniform aperture to enable the long interference baseline to obtain a high signal-to-noise ratio to enhance the clarity of high-frequency details. It can be used as a lightweight super-resolution remote sensing imaging system and a lightweight super-resolution imaging system, and has the advantages of short length, small size and light weight. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is a schematic structural diagram of an imaging system of the present invention;

[0015] Figure 2 is a graph showing the relationship between the visibility of interference fringes and the length of the interference baseline of the present invention;

[0016] Figure 3 is a light distribution diagram simulated by an embodiment;

[0017] Figure 4 is an imaging simulation image of a conventional optoelectronic imaging system in the embodiment;

[0018] Figure 5 It is an imaging simulation image in the embodiment which is different from the imaging simulation image using a uniform aperture microlens array in the present invention;

[0019] Figure 6 is a distribution curve diagram of the aperture values ​​of the microlenses on each interference baseline of the interference arm in the embodiment;

[0020] Figure 7 1 is an imaging simulation image of the imaging system of the present invention in an embodiment.

[0021] In the figure: 1, substrate; 2, interference arm; 2-1, non-uniform microlens line array group; 2-2, non-uniform microtube line array group; 2-3, coupled interference module group; 2-4, optical fiber; 2-1-1, microlens; 2-2-1, microtube; 2-3-1, coupled interference unit; 2-3-2, information processing module. DETAILED DESCRIPTION

[0022] The technical solution of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0023] like Figure 1 As shown, a non-uniform microlens array super-resolution planar interference photoelectric imaging system includes a substrate 1 and a plurality of interference arms 2. The surface of the substrate 1 is uniformly fixed with a plurality of identical interference arms 2 in an annular direction, and the plurality of interference arms 2 are arranged radially. Wherein, the middle layer of each interference arm 2 is a non-uniform microlens linear array group 2-1, and the non-uniform microlens linear array group 2-1 is composed of a plurality of microlenses 2-1-1, the number N of the plurality of microlenses 2-1-1 is an even number, the plurality of microlenses 2-1-1 are arranged along the center line in a mirror-symmetrical manner, and the aperture of the microlenses 2-1-1 is set to decrease from both ends to the middle, and each two mirror-symmetrical microlenses 2-1-1 are paired (for example, the microlenses are numbered from 1 to N from one end to the other end, then the microlens No. 1 at the outermost end is paired with the microlens No. N, and then paired in sequence from the outermost end to the inner side until the microlens No. N / 2 in the middle is paired with the microlens No. 1+N / 2) and form an interference baseline, the length of the interference baseline is equal to the center distance between the corresponding two microlenses 2-1-1, therefore, the two microlenses 2-1-1 at the outermost end form a length B of the longest interference baseline. max The length B of the shortest interference baseline formed by the two middle microlenses 2-1-1 min ; The top layer of each interference arm 2 is a non-uniform micro-pipeline array group 2-2, which is composed of a plurality of micro-pipes 2-2-1, and the plurality of micro-pipes 2-2-1 are arranged one-to-one with a plurality of micro-lenses 2-1-1, and each micro-tube 2-2-1 has the same caliber as the corresponding micro-lens 2-1-1 and is coaxially arranged; the bottom layer of each interference arm 2 is a coupling interference module group 2-3, and the coupling interference module group 2-3 is composed of an information processing module 2-3-2 and a plurality of coupling interference units 2-3-1, and the number of the plurality of coupling interference units 2-3-1 is N / 2, and each pair of two micro-lenses 2-1-1 is connected to an input end of a coupling interference unit 2-3-1 through an optical fiber 2-4, and the information processing module 2-3-2 is connected to the output ends of all coupling interference units 2-3-1 through an optical fiber 2-4. The two microlenses 2-1-1 on the interference baseline transmit the optical signal to the corresponding coupling interference unit 2-3-1 through the optical fiber 2-4 at the rear focus for spectral splitting and coherent superposition to form interference fringes. The information processing module 2-3-2 converts the interference fringes output by the N / 2 coupling interference units 2-3-1 of the interference arm 2 into electrical signals.

[0024] After the information processing modules 2-3-2 of all the interference arms 2 of the imaging system of the present invention convert the interference fringes output by all the coupled interference module groups 2-3 into electrical signals, the imaging image can be obtained by uniformly performing inverse Fourier transform on the electrical signals.

[0025] The intensities of the light signals collected by the two microlenses 2-1-1 on the interference baseline are respectively I1 and I2. The interference light intensity I formed after entering the coupling interference module group 2-3 is expressed as follows:

[0026]

[0027] In the formula, γ 12 is the mutual interference function of the two light beams, φ is the phase difference between the two light beams, and λ is the central wavelength of the imaging band.

[0028] Then the interference fringe visibility V is expressed as follows:

[0029]

[0030] According to the van Heeter-Zernike theorem, the mutual interference function γ 12 It is expressed as follows:

[0031]

[0032] Where O(x, y, λ) is the two-dimensional light field distribution of the object, z is the object distance, and B x and B y are the components of the interference baseline in the x and y coordinate axes, respectively, and i is an imaginary unit. Therefore, as long as the interference fringes are detected, the imaging image of the observed scene can be obtained, which is different from the imaging mechanism of the traditional optoelectronic system.

[0033] The cutoff frequency u of the planar interferometric imaging system on the object side max_s It can be expressed as:

[0034]

[0035] In the formula, B max is the length of the longest interference baseline. It can be seen that the cutoff frequency of the planar interferometric imaging system has nothing to do with the pixel size of the detector.

[0036] Limited by the sampling effect of the photodetector, the cutoff frequency of the traditional diffraction-limited photoelectric imaging system in the image side is determined by the pixel side length a of the detector. According to the geometric relationship between the object and the image, the object side cutoff frequency u of the traditional diffraction-limited photoelectric imaging system is max_oe It can be expressed as:

[0037]

[0038] Where f is the focal length of the diffraction-limited optoelectronic imaging system. max_s >u max_oe When , the planar interferometric imaging system can obtain a higher resolution than the traditional diffraction-limited optoelectronic imaging system. From formula (4) and formula (5), the super-resolution imaging condition can be obtained as follows:

[0039]

[0040] The resolution of the imaging system of the present invention is max is proportional to, therefore, B max The larger it is, the higher its resolution.

[0041] For a traditional diffraction-limited optoelectronic imaging system with a = 5 μm and f = 100 mm, when the central wavelength λ = 1 μm and the object distance z = 1 m, the length of the longest interference baseline satisfies B max When the image size is >10mm, a higher resolution than that of conventional optoelectronic imaging systems can be achieved.

[0042] Since the interference arms 2 of the imaging system of the present invention are arranged uniformly in the annular direction and have rotational symmetry, only one interference arm 2 is required for analysis. For the center distance of the two microlenses 2-1-1 arranged on one interference arm 2 in the x direction, B x , a quasi-monochromatic slit light source with a width of δ = 2 μm is used, the distance between the light source and the two microlenses 2-1-1 is equal, and the radiation intensity is evenly distributed, then I1 = I2, and formula (2) and formula (3) can be simplified after being combined as follows:

[0043]

[0044] Using the same central wavelength λ = 1 μm and object distance z = 1 m, we can substitute into formula (7):

[0045]

[0046] like Figure 2 As shown, according to formula (8), V and B are plotted x It can be seen that as B x As the interference fringes increase, V decreases significantly. Since there is noise in the formation of interference fringes and the photoelectric conversion process, the lower the visibility of the interference fringes, the lower the signal-to-noise ratio of the interference baseline detection signal. In order to improve the signal-to-noise ratio of the interference baseline detection signal, it is necessary to follow Figure 2 The light transmission area of ​​the microlens 2-1-1 on each interference arm 2 is set according to the inverse rule of the middle curve.

[0047] Example

[0048] The advantages of the imaging system of the present invention are explained by combining imaging simulation examples, as follows:

[0049] Figure 3 The light distribution diagram of the observation scene example simulation is given, the object distance z is 1m, and the wavelength of the light wave radiation is 0.8~1.2μm.

[0050] Figure 4An imaging simulation image of a traditional diffraction-limited optoelectronic imaging system with an aperture of D = 200 mm, a focal length of f = 100 mm, and a detector pixel side length of a = 5 μm is given. It can be seen that due to the limitation of the detector pixel side length, the high-frequency details in the middle part of the image are severely lost and the image details are very blurred.

[0051] Figure 5 The imaging simulation images of a planar interference optoelectronic imaging system based on a uniform aperture (all apertures are consistent) microlens array when there is a noise of 5% of the maximum light intensity are given. The system parameters are shown in Table 1:

[0052] Table 1 Parameters of the planar interferometric optoelectronic imaging system based on uniform aperture microlens array

[0053]

[0054] It can be seen that due to the length of the longest interference baseline B max It reaches 400mm, which is much higher than the super-resolution condition given by formula (6). The high-frequency details in the middle part of the image are Figure 4 The image is rich and the details are clear, but due to the existence of noise, the high-frequency components collected by the long interferometer baseline are more seriously interfered by noise than the low-frequency components, resulting in lower clarity of high-frequency details than low-frequency details.

[0055] In order to improve the signal-to-noise ratio of the high-frequency components collected by the long interference baseline, it is necessary to increase the light intensity collected by the microlens 2-1-1 on the long interference baseline. Under the same noise conditions, the signal-to-noise ratio of the interference fringes is proportional to the intensity of the light signal. Increasing the light-passing area can increase the light intensity collected by the microlens 2-1-1, thereby improving the signal-to-noise ratio. Since the visibility of the interference fringes increases with the increase of the interference baseline length, Figure 2 The curve decays regularly, and the signal-to-noise ratio also decays according to Figure 2 To ensure that the signal-to-noise ratio does not decay with the increase of the interference baseline length, the intensity of the optical signal needs to be Figure 2 The inverse of the middle curve increases, so the light transmission area of ​​microlens 2-1-1 should be Figure 2 The reciprocal law of the curve increases. The light transmission area of ​​the microlens 2-1-1 is proportional to the square of its aperture. Therefore, the aperture of the microlens 2-1-1 on the interference baseline of different lengths should be Figure 2 The interference fringe visibility curve shown changes according to the square root rule of the reciprocal.

[0056] Except for the aperture d of the microlens 2-1-1, the parameters of the imaging system of the present invention are consistent with those in Table 1. Since the number N of the microlenses 2-1-1 on each interference arm 2 in Table 1 is 100, the number of interference baselines is half of it, and the apertures of the two microlenses 2-1-1 on the same interference baseline are consistent, the aperture d value of the microlens 2-1-1 on each interference arm 2 is 50.

[0057] Figure 6 The aperture d value of the microlens 2-1-1 on the 50 interference baselines of each interference arm 2 is given. As the length of the interference baseline increases, the aperture d value increases according to Figure 2 The square root value of the reciprocal of the curve increases.

[0058] Figure 7 The imaging simulation image of the imaging system of the present invention when there is 5% of the maximum light intensity noise is given. It can be seen that the increase in the aperture of the long baseline microlens 2-1-1 increases the collected light intensity, thereby improving the signal-to-noise ratio of the interference fringes, and the high-frequency details in the image are better than those in the conventional imaging system. Figure 5 Clear, and the clarity of high-frequency details is basically the same as that of low frequencies.

[0059] In summary, it can be proved that the imaging system of the present invention can not only obtain a higher resolution than the traditional optoelectronic imaging system, but also the high-frequency detail components are very clear, and the imaging performance is very superior.

[0060] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other forms of assembly without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-restrictive, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations within the meaning and range of equivalents of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0061] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A non-uniform microlens array super-resolution planar interferometric photoelectric imaging system, characterized in that: The invention comprises a substrate (1) and a plurality of interference arms (2), wherein the plurality of interference arms (2) are evenly fixed in an annular direction on the surface of the substrate (1), and the plurality of interference arms (2) are arranged radially, and the middle layer of each interference arm (2) is composed of a plurality of micro lenses (2-1-1) of an even number, and the plurality of micro lenses (2-1-1) are arranged in a mirror-symmetrical manner along a center line and the apertures are arranged in a decreasing manner from both ends to the middle, and each of the two mirror-symmetrical micro lenses (2-1-1) is matched into a pair and forms an interference baseline, and the top layer of each interference arm (2) is composed of a plurality of micro tubes (2-2 -1), the plurality of microtubes (2-2-1) and corresponding microlenses (2-1-1) have the same caliber and are coaxially arranged, the bottom layer of each interference arm (2) is composed of an information processing module (2-3-2) and a plurality of coupling interference units (2-3-1), each pair of two microlenses (2-1-1) is connected to an input end of a coupling interference unit (2-3-1) via an optical fiber (2-4), and the information processing module (2-3-2) is connected to the output ends of the plurality of coupling interference units (2-3-1) via an optical fiber (2-4).

2. The non-uniform microlens array super-resolution planar interferometric photoelectric imaging system according to claim 1, characterized in that: The super-resolution imaging conditions of the imaging system are: In the formula, B max is the length of the longest interference baseline, f is the focal length of the diffraction limited optoelectronic imaging system, λ is the central wavelength of the imaging band, and a is the side length of the detector pixel of the diffraction limited optoelectronic imaging system.

3. The non-uniform microlens array super-resolution planar interferometric photoelectric imaging system according to claim 2, characterized in that: The two microlenses (2-1-1) on the interference baseline transmit the optical signal to the corresponding coupling interference unit (2-3-1) through the optical fiber (2-4) at the rear focus for spectral beam splitting and coherent superposition to form interference fringes. The information processing modules (2-3-2) of all the interference arms (2) respectively convert the interference fringes output by the corresponding plurality of coupling interference units (2-3-1) into electrical signals, and then uniformly perform inverse Fourier transform on the electrical signals to obtain an imaging image.

4. The non-uniform microlens array super-resolution planar interferometric photoelectric imaging system according to claim 3, characterized in that: Assume that the visibility of the interference fringes is V, and the component of the interference baseline in the x-axis direction is B. x , plot V and B x The relationship curve of the plurality of microlenses (2-1-1) on the interference arm (2) increases with the increase of the interference baseline length, and the aperture value of the microlens (2-1-1) increases according to the square root value of the inverse of the visibility of the interference fringes in the relationship curve.

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