Planar interferometric optoelectronic system for visible light imaging

Abstract

This invention discloses a planar interferometric optoelectronic system for visible light imaging. The system comprises a microtube array, a microlens array, an optoelectronic module group, and a substrate. The microtube array blocks stray light; the microlens array collects light; the optoelectronic module group performs baseline pairing, narrowband filtering of the visible light band, coupling interference, and information processing; and the substrate provides fixed support for the entire planar interferometric optoelectronic system. This planar interferometric optoelectronic system uses micro / nano optical filters instead of arrayed waveguide gratings to achieve tunable nanometer-scale ultra-narrow linewidth spectra across the entire visible light band. It can be used as a lightweight remote sensing imaging system and a lightweight visible light imaging system. This system offers advantages such as short length, small size, light weight, wide imaging spectral range, and fast response speed for imaging in the visible light band.

Description

Technical Field

[0001] This invention belongs to the fields of interferometric imaging and micro-nano optics, and relates to a planar interferometric optoelectronic system, specifically a visible light band planar interferometric optoelectronic imaging system based on interferometric imaging and micro-nano optics technology. Background Technology

[0002] To significantly reduce the length, volume, and weight of optical imaging systems, the United States proposed a planar interferometric optoelectronic imaging system in 2012. This system uses a microlens array to collect light, and implements interference pairing, phase adjustment, waveguide coupling, and coherent detection within a photonic integrated circuit. After signal processing, a spatial image is obtained, reducing the length, volume, and weight of the optical system by 10 to 100 times. To achieve good interferometric results, the system uses an arrayed waveguide grating to filter out a narrow-band spectrum with nanometer-scale linewidths from the incident light band. However, arrayed waveguide gratings can only operate in the near-infrared optical communication band (1540 nm–1600 nm). Due to the significant energy loss of the arrayed waveguide grating when operating in the visible light band, this system currently cannot image in the visible light band. Since the wavelength of visible light is much shorter than that of near-infrared light, the imaging resolution in the visible light band is much higher than that in the near-infrared band. Therefore, researching a planar interferometric optoelectronic system for visible light imaging has significant theoretical and practical value. Summary of the Invention

[0003] This invention provides a planar interferometric optoelectronic system for imaging in the visible light band. This system uses micro-nano optical filters instead of arrayed waveguide gratings to achieve a tunable nanometer-scale ultranarrow linewidth spectrum across the entire visible light band.

[0004] The objective of this invention is achieved through the following technical solution:

[0005] A planar interferometric optoelectronic system for visible light imaging comprises multiple interferometer arms. Each interferometer arm includes a microlens array and a photoelectric module group. Above each microlens array is a microtube array to block stray light. The photoelectric module group of each interferometer arm includes a set of micro / nano optical filters, a set of coupling modules, and an information processing module. Every two microlenses on each interferometer arm are paired to form an interference baseline. Light radiation is collected by the microlens array and then irradiates the surface of the set of micro / nano optical filters at a given angle. The micro / nano optical filter group converts the incident light into an ultra-narrowband spectrum at the nanometer scale in the visible light band. The ultra-narrowband spectrum of the same wavelength obtained by a pair of microlenses enters a coupling module and forms interference fringes. The interference fringes are converted into electrical signals by a photodetector in the coupling module, changing the incident angle of the light to the micro / nano optical filter group to obtain electrical signals converted by interference at different wavelengths. The coupling module group combines the electrical signals into spectral data and performs an inverse Fourier transform in the information processing module to form an image.

[0006] Compared with the prior art, the present invention has the following advantages:

[0007] The planar interferometric photoelectric system of the present invention can be used as a lightweight remote sensing imaging system and a lightweight visible light imaging system. This system images in the visible light band and has the advantages of short length, small size, light weight, large imaging spectral range and fast response speed. Attached Figure Description

[0008] Figure 1 This is a structural diagram of a planar interferometric optoelectronic system used for imaging in the visible light band, and a partial interferometer arm.

[0009] Figure 2 This is a structural diagram of a micro / nano optical filter.

[0010] Figure 3 The output spectrum of a micro / nano optical filter;

[0011] Figure 4 This is a structural diagram of a coupled module;

[0012] Figure 5 This is a structural diagram of a liquid crystal phase delayer.

[0013] Figure 6 A light distribution map of the observed scene instance;

[0014] Figure 7 This is an image of the observed scene obtained by a planar interferometric optoelectronic system used for imaging in the visible light band. Detailed Implementation

[0015] The technical solution of the present invention will be further described below with reference to the accompanying drawings, but it is not limited thereto. Any modifications or equivalent substitutions to the technical solution of the present invention that do not depart from the spirit and scope of the technical solution of the present invention should be covered within the protection scope of the present invention.

[0016] This invention provides a planar interferometric optoelectronic system for imaging in the visible light band, such as... Figure 1 As shown, the planar interference optoelectronic system consists of a microtube array, a microlens array, optoelectronic modules, and a substrate, wherein: the microtube array is used to block stray light; the microlens array is used to collect light; the optoelectronic module group is used to complete baseline pairing, visible light narrowband filtering, coupling interference, and information processing; and the substrate is used to fix and support the entire planar interference optoelectronic system.

[0017] like Figure 1As shown, the planar interferometric optoelectronic system for visible light imaging consists of multiple interferometer arms. Each interferometer arm's optoelectronic module group includes a set of micro / nano optical filters, a set of coupling modules, and an information processing module. Every two microlenses on each interferometer arm are paired to form an interference baseline. Light radiation is collected by the microlens array and then irradiated onto the surface of a set of micro / nano optical filters at a given angle. The micro / nano optical filter group converts the incident light into an ultra-narrowband spectrum at the nanometer scale in the visible light band. The ultra-narrowband spectrum of the same wavelength obtained by each pair of microlenses enters a coupling module and forms interference fringes. These interference fringes are converted into electrical signals by a photodetector in the coupling module, changing the incident angle of the light to the micro / nano optical filter group to obtain electrical signals converted by interference at different wavelengths. The coupling module group combines the electrical signals into spectral data and performs an inverse Fourier transform in the information processing module to form an image.

[0018] like Figure 2 As shown, the micro-nano optical filter in the optoelectronic module consists of, from top to bottom, a one-dimensional subwavelength grating layer with a refractive index of 1.61, a first thin film layer with a refractive index of 2.06, a second thin film layer with a refractive index of 1.81, and a substrate with a refractive index of 1.51. The thicknesses of the one-dimensional subwavelength grating layer, the first thin film layer, the second thin film layer, and the substrate are 92.9 nm, 54.9 nm, 60.8 nm, and 2 mm, respectively. The period and linewidth of the one-dimensional subwavelength grating layer are 265 nm and 132.5 nm, respectively.

[0019] like Figure 3 As shown, when light collected by the microlens array is incident on the micro-nano optical filter at different incident angles, the linewidth of the output spectrum does not exceed 2 nm. By changing the incident angle, the narrowband spectrum can be tuned, and the spectral tuning range covers the entire visible light band. When the incident angle changes continuously from small to large, the peak wavelength of the spectrum shifts linearly from short to long wavelengths within the visible light wavelength range.

[0020] like Figure 4 As shown, the coupling module includes a 2×2 multimode fiber waveguide structure, a liquid crystal phase delayer, and photodetectors A, B, C, and D. Figure 5As shown, a liquid crystal (LC) phase retarder with a response speed on the order of milliseconds is used to improve the response speed of the coupling module. The fabrication principle of the LC phase retarder involves depositing an indium tin oxide (ITO) film with a thickness of approximately 200 nm on two transparent substrates, followed by a polyimide (PI) film. The two PI films in the LC phase retarder are rubbed in the same direction. Finally, SiO2 microspheres with a diameter of 10–100 μm are used to separate the two PI film layers, and the LC is injected and sealed. Applying a voltage to the two ITO film layers changes the refractive index of the LC layer, thereby achieving rapid phase delay. After combining the LC phase retarder with an optical fiber coupler, interference fringes are produced. The response speed of this PIC structure depends on the LC phase retarder; by improving the fabrication process of the LC phase retarder, the response speed can be increased to the order of milliseconds.

[0021] The coupling module is used to acquire the amplitude and phase information of the interference fringes. After photoelectric conversion, the resulting spectral data is used to convert it into an image. The complex visibility of the interference fringes can be expressed as:

[0022]

[0023] Where λ is the center wavelength of each spectral channel, z is the object distance, and B x B y Let O(x,y,λ) be the components of the interference baseline along the x and y coordinate axes, and O(x,y,λ) be the two-dimensional light field distribution corresponding to the wavelength λ of the object. The cutoff frequency u of the planar interferometric imaging system on the object side... max It can be represented as:

[0024]

[0025] Where λ is the average wavelength, B max The length of the longest interference baseline. Optical signals S and R pass through the two input ends of a 2×2 multimode fiber waveguide structure, and are then split into two optical signals. The two signals from the split optical signal S are in phase, while one of the two signals from the split optical signal R experiences a 90° phase delay. Therefore, the two signals from the split optical signal R are orthogonal in phase. After coherent superposition, the photocurrents generated by photodetectors A, B, C, and D are as follows:

[0026]

[0027] Where E1(t) is the amplitude of signal S, E2(t) is the amplitude of signal R, k1 and φ1 are the wave vector and phase of optical signal S, k2 and φ2 are the wave vector and phase of optical signal R, ω is the angular frequency of the light wave, and φ1 = αk1 and φ2 = αk2.

[0028] The output signals I(t) and Q(t) are respectively:

[0029] I(t)=I A (t)-I B (t)=4E1E2 cos(α·k) (7)

[0030] Q(t) = I C (t)-I D (t)=4E1E2 cos(α·k+π / 2) (8)

[0031] Where k = k1 - k2. The amplitudes E1 and E2, and the phase φ = αk can be calculated using the following formulas:

[0032]

[0033] The amplitude and phase of the interference fringes are obtained by formulas (3) to (10).

[0034] Imaging simulations were performed on a planar interferometric optoelectronic system for visible light imaging using the parameters shown in Table 1. Figure 6 The image shown is a light distribution map of an example of the observed scene. Figure 7 The image shown is an image of the observed scene obtained by a planar interferometric photoelectric system used for visible light imaging.

[0035] Table 1. Parameters of the planar interferometric optoelectronic system used for visible light imaging.

[0036]

[0037]

Claims

1. A planar interferometric optoelectronic system for imaging in the visible light band, characterized in that... The system includes multiple interferometer arms, each comprising a microlens array and a photoelectric module group. Above each microlens array is a microtube array used to block stray light. Each interferometer arm's photoelectric module group includes a set of micro / nano optical filters, a coupling module, and an information processing module. Every two microlenses on each interferometer arm pair to form an interference baseline. Light radiation is collected by the microlens array and then irradiated onto the surface of the micro / nano optical filters at a given angle. The micro / nano optical filters convert the incident light into an ultra-narrowband spectrum at the nanometer scale in the visible light band. The ultra-narrowband spectra of the same wavelength obtained by a pair of microlenses enter a coupling module to form interference fringes. These interference fringes are converted into electrical signals by a photodetector in the coupling module, changing the incident angle of the light to the micro / nano optical filters to obtain electrical signals converted from different wavelengths of interference. The coupling module group combines the electrical signals into spectral data, and performs an inverse Fourier transform in the information processing module to form an image. The linewidth of the output spectrum of the light collected by the microlens array when it irradiates the micro-nano optical filter at different incident angles does not exceed 2nm. By changing the incident angle, the narrowband spectrum can be tuned and the spectral tuning range covers the entire visible light band. The micro-nano optical filter is composed of, from top to bottom, a one-dimensional subwavelength grating layer with a refractive index of 1.61, a first thin film layer with a refractive index of 2.06, a second thin film layer with a refractive index of 1.81, and a substrate with a refractive index of 1.

51. The thicknesses of the one-dimensional subwavelength grating layer, the first thin film layer, the second thin film layer, and the substrate are 92.9 nm, 54.9 nm, 60.8 nm, and 2 mm, respectively, and the period and grating linewidth of the one-dimensional subwavelength grating layer are 265 nm and 132.5 nm, respectively.

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