Optical device, method for manufacturing an optical device, and use thereof

Abstract

The application discloses an optical device, a preparation method of the optical device and application of the optical device, and relates to a double-twist liquid crystal polymer layer, a light orientation layer and a transparent substrate layer; the light orientation layer is arranged on the transparent substrate layer, and the double-twist liquid crystal polymer layer is arranged on the light orientation layer; a pure phase distribution is recorded on the light orientation layer; and the double-twist liquid crystal polymer layer comprises two stacked liquid crystal layers with opposite chirality. The application realizes high diffraction efficiency in a wideband visible spectrum, effectively overcomes the inherent chromatic aberration limitation of a traditional diffraction lens, expands the application range of the diffraction lens, and no longer limits the simple imaging function, so that the complexity and cost of a multi-spectrum imaging system, machine vision and a full-optical computing system are greatly reduced.

Description

Technical Field

[0001] This invention relates to the fields of micro-nano optics and computational imaging technology, and in particular to an optical device, a method for fabricating the optical device, and its applications. Background Technology

[0002] Recently, the rapid development of emerging fields such as artificial intelligence, bioengineering, and quantum computing has presented unprecedented challenges to real-time, high-speed, and high-precision data processing. Traditional information processing architectures rely on "optical-electrical-optical" conversions, where information is transmitted as optical signals but processed using electrical signals. This method suffers from drawbacks such as high power consumption and slow processing speed. To address these challenges, all-optical analog computing (AOC) technology is receiving increasing attention. Spatial optical difference, as a key image processing operation, has proven effective in extracting image edges and enhancing details, showing broad application prospects in pattern recognition, object detection, and computational imaging.

[0003] However, traditional differential systems typically consist of numerous optical components (such as 4f Fourier systems), leading to functional limitations and integration difficulties. In recent years, while metasurfaces and liquid crystal materials have enabled device miniaturization, directly integrating lens phase and difference factors and eliminating the need for 4f systems, these differential lenses often lack chromatic aberration capabilities. During multispectral imaging, the inherent chromatic aberration of traditional diffractive lenses necessitates manual recalibration of the imaging position, inevitably limiting the practical application of differential systems. Therefore, developing a compact, chromatic aberration-free spatial differential device capable of efficient operation in the broadband visible spectrum has become a pressing need. Summary of the Invention

[0004] This invention proposes an optical device that can be used for multispectral computational imaging and all-optical signal processing. It overcomes the limitations of traditional diffractive differential lenses, such as lack of achromatic capability and large system size, and realizes a monolithic, compact, and highly diffractive double-twisted liquid crystal multi-wavelength multiplexed differential lens, which greatly reduces the integration difficulty of related optical imaging systems.

[0005] The technical solution to achieve the purpose of this invention is as follows: an optical device, comprising a double-twisted liquid crystal polymer layer, a light alignment layer, and a transparent substrate layer; the light alignment layer is disposed on the transparent substrate layer, and the double-twisted liquid crystal polymer layer is disposed on the light alignment layer; a pure phase distribution is recorded on the light alignment layer; the double-twisted liquid crystal polymer layer comprises two stacked liquid crystal layers with opposite chirality.

[0006] Preferably, the double-twisted liquid crystal polymer layer comprises two liquid crystal polymer mixture layers with the same thickness and opposite twist angles.

[0007] Preferably, the pure phase distribution is synthesized by combining the complex amplitude difference factor and the phase of the multi-wavelength achromatic lens using a dual-phase encoding method, specifically as follows:

[0008]

[0009] In the formula, φ LR , φ LG and φ LB θ represents the focusing phase that achieves the achromatic function of the target wavelength, and θ represents the complex amplitude difference factor.

[0010] This invention also proposes a method for fabricating an optical device, comprising:

[0011] Calculate the required complex amplitude difference factor and multi-wavelength achromatic lens phase based on the target difference order and lens focal length;

[0012] The complex amplitude difference factor and the phase of the multi-wavelength achromatic lens are synthesized into a pure phase distribution using a dual-phase encoding method.

[0013] The synthesized pure phase distribution is recorded onto a photo-alignment layer spin-coated on a transparent substrate using photolithography.

[0014] A double-twisted liquid crystal polymer layer is fabricated on the photo-alignment layer to form the optical device.

[0015] The present invention also proposes an application of an optical device for use in multispectral computational imaging, edge detection, or optical computing systems;

[0016] After the input target beam containing multiple wavelengths of RGB is modulated by the optical device, a colorless differential image with edge enhancement effect is directly output on a single imaging plane without the need for an additional 4f system and chromatic aberration correction lens group.

[0017] Compared with the prior art, the present invention has the following significant advantages: Compared with the prior art, the embodiments of the present invention effectively solve the problem of focal length shift caused by the change of wavelength of diffraction lens, and can directly capture the spatial derivative image of red, green and blue (RGB) three channels on a plane without manual refocusing; at the same time, due to the use of direct processing in the all-optical simulation domain, the device size is significantly reduced, and the flexibility and computational efficiency of devices in cutting-edge photonics fields such as multispectral machine vision and label-free biological imaging are greatly improved.

[0018] The present invention will now be described in further detail with reference to the accompanying drawings. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a 3D schematic diagram and a magnified view of a partial molecular arrangement of a double-twisted liquid crystal (DTLC) lens structure provided in an embodiment of the present invention.

[0021] Figure 2 This invention relates to the principle of complex amplitude difference factor dual-phase encoding synthesis and the final pure phase distribution diagram provided in the embodiments of the present invention.

[0022] Figure 3 This is a simulation diagram of the parameter optimization (thickness and twist angle relationship) and broadband polarization conversion efficiency of the double-twisted liquid crystal structure provided in the embodiments of the present invention.

[0023] Figure 4 This is a simulation (Sim) and experimental (Exp) verification diagram of the light intensity distribution of the multi-wavelength achromatic differential lens in the light propagation direction provided in the embodiment of the present invention.

[0024] Figure 5 This is a comparison of the imaging effects of the optical device provided in this embodiment of the invention for multi-wavelength edge extraction of the letter "E" (including the target object, simulation and experimental results).

[0025] Figure 6 This is a verification diagram of the optical device provided in this embodiment of the invention performing multi-wavelength spatial coincidence differential imaging of the RGB three-color letters "NJU".

[0026] Figure 7 This is a schematic diagram of the principle of multi-level magnification (multi-focal length) spatial difference imaging based on a single wavelength, provided in an embodiment of the present invention.

[0027] Figure 8 This is a phase design and 3D beam propagation simulation diagram of off-axis color routing spatial difference implemented by additional dispersion vector encoding provided in the embodiments of the present invention.

[0028] Figure 9 This is an experimental verification result diagram of off-axis color routing spatial differential imaging provided in an embodiment of the present invention. Detailed Implementation

[0029] According to a first aspect of the present invention, an optical device is provided, comprising a double-twisted liquid crystal polymer layer, a light alignment layer, and a transparent substrate layer; the light alignment layer is disposed on the transparent substrate layer, and the double-twisted liquid crystal polymer layer is disposed on the light alignment layer; a pure phase distribution is recorded on the light alignment layer; the double-twisted liquid crystal polymer layer comprises two stacked liquid crystal layers with opposite chirality.

[0030] In a further embodiment, the double-twisted liquid crystal polymer layer is composed of two stacked liquid crystal polymer mixture layers of the same thickness but with opposite twist angles, such as... Figure 3 As shown on the left; the liquid crystal molecules of the liquid crystal polymer mixture liquid crystal layer are given a specific arrangement direction by the light alignment layer, thereby encoding a phase distribution with a specific function, the phase distribution including the phase of the multi-wavelength achromatic lens and the complex amplitude difference factor.

[0031] When a beam containing multiple wavelengths passes through a double-twisted liquid crystal polymer layer to modulate the phase and amplitude of different wavelength beams, the double-twisted liquid crystal polymer layer can achieve chromatic aberration-free multi-wavelength spatial difference imaging.

[0032] In a further embodiment, the pure phase distribution is synthesized by combining the complex amplitude difference factor and the phase of the multi-wavelength achromatic lens using a dual-phase encoding method, specifically:

[0033]

[0034] In the formula, φ LR , φ LG and φ LB θ represents the focusing phase that achieves the achromatic function of the target wavelength, and θ represents the complex amplitude difference factor.

[0035] Optionally, the complex amplitude difference factor is synthesized by a two-phase method, which decomposes the target complex amplitude into two pure phase components and performs pixel-level sampling and superposition using a complementary binary grating.

[0036] Optionally, the complex amplitude difference factor h(r, θ) = re iθ Includes the radially varying amplitude distribution r and the vortex phase e with a topological charge of +1. iθ It is used to realize first-order spatial optical difference.

[0037] Optionally, the phase of the multi-wavelength achromatic lens is suitable for wavelength multiplexing and achromatic focusing at at least three different wavelengths, including 470nm, 525nm and 647nm in the visible light band.

[0038] This invention combines the phase of a multi-wavelength achromatic lens with a complex amplitude difference factor, wherein the complex amplitude difference factor is encoded using a biphase method and incorporated into the overall phase distribution. When incident light containing multiple wavelengths (such as 470nm, 525nm, and 647nm) passes through this device, beams of specific wavelengths overlap in the spatial frequency domain and are differentially modulated, thereby directly forming a high-resolution edge extraction image on the same imaging plane without chromatic aberration.

[0039] According to a second aspect of the present invention, a method for fabricating an optical device is provided, comprising:

[0040] The complex amplitude difference factor θ and the phase arg (φ) of the multi-wavelength achromatic lens are calculated based on the target difference order and the lens focal length. LR + φ LG + φ LB ), where φ LR , φ LG and φ LB These represent the focusing phases that achieve the achromatic function at the target wavelength, and θ represents the complex amplitude difference factor.

[0041] The complex amplitude difference factor and the phase of the multi-wavelength achromatic lens are synthesized into a pure phase distribution using the dual-phase encoding method. ;

[0042] The synthesized pure phase distribution is recorded onto a photo-alignment layer spin-coated on a transparent substrate using photolithography.

[0043] A double-twisted liquid crystal polymer layer is fabricated on the light alignment layer that records phase information to form the optical device;

[0044] The double-twisted liquid crystal polymer layer includes, for example: Figure 3 The two stacked liquid crystal polymer mixture liquid crystal layers with opposite chirality shown on the left enable the light beam to have broadband high diffraction efficiency and achromatic differential modulation capability when it passes through.

[0045] Optionally, a double-twisted liquid crystal structure is fabricated on the light alignment layer recording phase information to form the optical device, comprising:

[0046] A first layer of liquid crystal polymer mixture with specific chirality (such as left-handedness) is coated onto the photo-alignment layer using spin coating technology and then cured under ultraviolet light; the liquid crystal polymer mixture has a thickness of about 14 micrometers and a twist angle of about 70°.

[0047] In some embodiments, the liquid crystal polymer mixture may be a liquid crystal polymer monomer, a photoinitiator, and a chiral agent.

[0048] A second layer of liquid crystal polymer mixture with opposite chirality (e.g., right-handedness) is spin-coated onto the surface of the cured first layer of liquid crystal polymer, followed by UV curing to obtain the double-twisted liquid crystal structure. The liquid crystal polymer mixture is approximately 14 micrometers thick, with a twist angle of approximately -70°, where positive and negative represent left-handedness and right-handedness.

[0049] According to a third aspect of the present invention, an application based on any of the optical devices described in the first aspect is provided, the optical devices being used in multispectral computational imaging, edge detection, or optical computing systems;

[0050] After the input target beam containing multiple wavelengths of RGB is modulated by the optical device, a colorless differential image with edge enhancement effect is directly output on a single imaging plane without the need for an additional 4f system and chromatic aberration correction lens group.

[0051] The optical device provided in this invention includes a phase modulation layer based on a double-twisted liquid crystal (DTLC) structure. By combining two liquid crystal layers of equal thickness but opposite twist angles, the device exhibits high polarization conversion efficiency (over 80%) in the visible spectrum (approximately 300 nm bandwidth), and superimposes the phase of a multi-wavelength achromatic lens and a complex amplitude difference factor encoded by a dual-phase method in the phase distribution.

[0052] When the target beam is a single wavelength, due to wavelength reuse and dispersion effects, the device exhibits multifocal characteristics in the beam propagation direction, thereby realizing edge extraction imaging based on a single device with flexible multi-level magnification (such as 1.32x, 1.88x and 4.00x).

[0053] Figure 1 This diagram illustrates a 3D schematic of the core structure of a double-twisted liquid crystal (DTLC) according to an embodiment of the present invention. The device employs a dual-layer liquid crystal architecture, comprising a bottom layer and a top layer of liquid crystal with equal thickness but opposite twist angles. Compared to traditional single-layer nematic liquid crystals, this structure exhibits a significant phase retardation compensation effect through the opposite molecular arrangement (as shown in the enlarged dashed box on the right), which is fundamental to achieving broadband high-efficiency diffraction.

[0054] Figure 2 This paper discloses a complex amplitude encoding method for the phase modulation layer of a device. Since first-order spatial differentiation requires complex amplitude modulation, this embodiment employs double-phase encoding. According to the formula... and The continuous amplitude and phase distributions can be decomposed into two sets of pure phase components. and Subsequently, these two phase distributions are spatially interleaved and recombined at the pixel level through complementary binary gratings (in the form of a black and white checkerboard), ultimately generating a single-layer pure phase distribution map (i.e., a hologram that can simultaneously modulate amplitude and phase) as shown on the far right.

[0055] Figure 3 The optimization process of the device's physical parameters is described in detail to achieve high diffraction efficiency across multiple wavelengths. The left side shows a model diagram of the double-twisted liquid crystal, where each liquid crystal layer has a thickness of D. The efficiency mapping diagram on the right shows the diffraction efficiency distribution of the device for three wavelengths (470 nm, 525 nm, and 647 nm) under different single-layer thicknesses D and twist angles φ. In this embodiment, the intersection of the white dashed lines (marked with a pentagram) in the diagram was selected as the optimal experimental parameters (e.g., D = 1.4 μm, φ = 7π / 18). Under these parameters, the device can maintain a very high level of circular polarization conversion efficiency across the entire visible spectrum.

[0056] Figure 4 The achromatic and differential focusing characteristics of the device were demonstrated. A comparison of experimental and simulation results shows that when beams of 647 nm (red), 525 nm (green), and 470 nm (blue) pass through the device, due to the precise phase compensation of the achromatic lens, the three beams are simultaneously focused onto the same confocal plane at z = 100 mm. Furthermore, the intensity distribution on the xy focal plane cross-section exhibits a typical hollow "donut" shape (point spread function), proving that the device successfully achieves isotropic first-order spatial difference operation.

[0057] Figure 5 and Figure 6 This demonstrates the device's edge detection (differentiation) capabilities in practical multi-wavelength image processing. Figure 5 In this study, using the letter "E" as the target object (Obj), both simulation (Sim) and experimental (Exp) results show that the device can clearly extract the outline edges of the letter from each of the RGB channels. Figure 6 When the input is a composite image "NJU" containing RGB colors, after one modulation by the device, a red, green and blue differential image with clear edges and precise spatial position can be directly captured on a single focal plane, completely eliminating image blurring and positional misalignment caused by color difference.

[0058] Figure 7This further demonstrates the device's flexible magnification and multifocal characteristics. Due to the lens's phase multiplexing and dispersion effects, under illumination at a single wavelength (e.g., 647 nm), the device generates multiple independent focal points (e.g., f1, f2, f3) along the optical axis. When an object (e.g., the letter "U") is placed in the optical path, edge extraction images at different magnifications (e.g., 1.32x, 1.88x, and 4.00x) can be obtained at these different focal planes. This provides a new solution for integrated, miniaturized, multi-level magnification optical microscopy systems.

[0059] Figure 8 and Figure 9 This demonstrates the application extension of the present invention in off-axis color routing spatial differential. For example... Figure 8 As shown on the left, by superimposing different wavelength-related tilted wave vectors (kr, kg, kb) into the phase of an achromatic lens, the device can guide beams of different wavelengths to different diffraction angles. Figure 8 The 3D propagation simulation diagram on the right verifies this design. The RGB three-color beams converge at z = 100 mm, but are separated into different spatial coordinates. Figure 9 The corresponding experimental results show that after inputting superimposed and overlapping color patterns, the device outputs spatially separated edge detection images of red "N", green "J", and blue "U". This design has extremely high application value in multi-channel image parallel processing and all-optical computing routing.

Claims

1. An optical device, characterized in that, It includes a double-twisted liquid crystal polymer layer, a light alignment layer, and a transparent substrate layer; the light alignment layer is disposed on the transparent substrate layer, and the double-twisted liquid crystal polymer layer is disposed on the light alignment layer; a pure phase distribution is recorded on the light alignment layer; the double-twisted liquid crystal polymer layer comprises two stacked liquid crystal layers with opposite chirality.

2. The optical device according to claim 1, characterized in that, The double-twisted liquid crystal polymer layer comprises two liquid crystal polymer mixture layers with the same thickness and opposite twist angles.

3. The optical device according to claim 2, characterized in that, The thickness of the liquid crystal layer of the liquid crystal polymer mixture is 14±0.5 micrometers, and the twist angle is 70°±2.5°.

4. The optical device according to claim 1, characterized in that, The liquid crystal polymer mixture is any one of liquid crystal polymer monomers, photoinitiators, and chiral agents.

5. The optical device according to claim 1, characterized in that, The pure phase distribution is synthesized by combining the complex amplitude difference factor and the phase of the multi-wavelength achromatic lens using a dual-phase encoding method, specifically: In the formula, φ LR , φ LG and φ LB θ represents the focusing phase that achieves the achromatic function of the target wavelength, and θ represents the complex amplitude difference factor.

6. The optical device according to claim 5, characterized in that, The complex amplitude difference factor includes a radially varying amplitude distribution and a vortex phase with a topological charge of +1, used to achieve first-order spatial optical difference.

7. A method for fabricating an optical device, used to fabricate the optical device as described in any one of claims 1-6, characterized in that, include: Calculate the required complex amplitude difference factor and multi-wavelength achromatic lens phase based on the target difference order and lens focal length; The complex amplitude difference factor and the phase of the multi-wavelength achromatic lens are synthesized into a pure phase distribution using a dual-phase encoding method. The synthesized pure phase distribution is recorded onto a photo-alignment layer spin-coated on a transparent substrate using photolithography. A double-twisted liquid crystal polymer layer is fabricated on the photo-alignment layer to form the optical device.

8. The method for fabricating an optical device according to claim 7, characterized in that, The double-twisted liquid crystal polymer layer comprises two liquid crystal polymer mixture layers with the same thickness and opposite twist angles.

9. The preparation method according to claim 7, characterized in that, A double-twisted liquid crystal polymer layer is fabricated on the photo-alignment layer to form the optical device, comprising: A first layer of a liquid crystal polymer mixture with a predetermined chirality is coated onto the photoalignment layer using spin coating technology, followed by UV curing. On the surface of the first layer of liquid crystal polymer after curing, a second layer of liquid crystal polymer mixture with the opposite chirality to the set chirality is spin-coated, and then UV cured.

10. An application based on the optical device according to any one of claims 1 to 6, characterized in that, The optical device is used in multispectral computational imaging, edge detection, or optical computing systems; After the input target beam containing multiple wavelengths of RGB is modulated by the optical device, a colorless differential image with edge enhancement effect is directly output on a single imaging plane without the need for an additional 4f system and chromatic aberration correction lens group.

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