Method and apparatus of full vectorial field detection for transparent planar devices

Abstract

This invention provides a method and apparatus for full-vector field detection of transparent planar elements with micro / nano structures, applicable to the full-field wavefront and polarization characteristics detection of planar optical elements such as metalenses and glass substrate apertures. This method utilizes digital holography to achieve high-resolution, full-field detection of the amplitude, phase, and polarization state of the transmitted light wave from a micro / nano structure planar element sample. The apparatus uses a digital holographic microscope architecture to capture two sets of interference patterns formed by the transmitted beam and a reference beam of the planar element sample with orthogonal polarization directions, performing holographic wavefront reconstruction and polarization state calculation. Through the method and apparatus provided by this invention, not only can the wavefront phase distribution of micro / nano structure planar elements be accurately measured, but their polarization modulation characteristics can also be simultaneously acquired, providing comprehensive and accurate quantitative data for the design optimization, process improvement, and performance evaluation of planar optical elements.

Description

[Technical Field]

[0001] This invention relates to full-vector field detection, and in particular to a method and apparatus for full-vector field detection of transparent planar elements. [Previous Technology]

[0002] In recent years, due to significant advancements in nanomaterials and manufacturing processes, metaplanar optical elements, with their nanoscale microstructures, possess diverse optical control characteristics and application potential, enabling arbitrary manipulation of light waves' phase, amplitude, polarization, and other parameters. This has garnered considerable attention and investment from the scientific and industrial communities both domestically and internationally. Metalenses will be a crucial and highly promising planar optical element in this field. These next-generation metaplanar elements, characterized by their small size and lightweight design, are expected to have the potential to largely replace bulky traditional glass / plastic lenses and lenses currently used in 3C smart products, optical imaging, and biomedical imaging systems.

[0003] However, existing wavefront detection technologies, such as the Shack-Hartmann wavefront sensor and interferometer architecture, cannot accurately measure the wavefronts of micro / nano-structured planar elements and their discontinuous step-wise wavefronts. Furthermore, errors in the accompanying collimating optical system or imaging system can easily lead to measurement aberrations, increased complexity of the alignment optical path, and time-consuming wavefront iteration calculations. In summary, existing wavefront detection technologies cannot meet the requirements for precise and accurate rapid wavefront analysis and polarization characteristic measurement of the full vectorial field. The method and apparatus for full vectorial field detection of transparent planar elements of this invention can be applied to the needs of planar element design, manufacturing, and commercialization processes, as well as to optimize the commercialization of such elements. [Summary of the Invention]

[0004] To achieve the above objective, the present invention proposes a method for full-vector field detection of a transparent planar element, comprising: providing a digital holographic microscope system, including at least a light source, a first beam splitter, an objective lens, a second beam splitter, at least one rotatable polarizing element, and at least one image sensor; splitting the light beam generated by the light source into an object beam and a reference beam by the first beam splitter; guiding the object beam through a transparent planar element under test; guiding the object beam and the reference beam through at least one polarizing element to generate two sets of interference patterns with orthogonal polarization directions on at least one image sensor; recording the interference patterns with the two sets of orthogonal polarization directions as a digital hologram using at least one image sensor; performing numerical reconstruction on the digital hologram using a digital computer to obtain amplitude and phase information of the transmitted light wave of the transparent planar element under test in two orthogonal polarization directions; and calculating the full-field wavefront amplitude, phase distribution, and polarization state of the transparent planar element under test using the obtained amplitude and phase information by the digital computer.

[0005] In one embodiment, the transparent planar element to be tested includes a combination of a super-lens and a glass substrate via.

[0006] The above-described method for full-vector field detection of a transparent planar element includes calculating the wavefront aberration function and the Strehl ratio using a digital computer based on the obtained full-field wavefront phase distribution, in order to evaluate the imaging quality of the transparent planar element under test. In one embodiment, the numerical reconstruction method includes the Fresnel diffraction approximation, Fourier transform, decomposition, or angular spectrum method.

[0007] In one embodiment, the first beam splitter is a polarized beam splitter or a non-polarized beam splitter. An objective lens is disposed in the optical path of the object beam and located between the first and second beam splitters to collect the object beam transmitted through the transparent planar element under test and to magnify the image of the transparent planar element under test. At least one rotatable polarizing element can be replaced by a waveplate element. The second beam splitter is a non-polarized beam splitter, disposed between the objective lens and at least one image sensor, to receive the object beam and reference beam penetrating the transparent planar element under test. At least one rotatable polarizing or waveplate element is disposed between the second beam splitter and at least one image sensor to generate superimposed interference of the object beam and reference beam with orthogonal polarization directions.

[0008] The present invention also includes another object: an apparatus for detecting the total vector field of a transparent planar element, comprising: a light source for generating a light beam; a first beam splitter for splitting the light beam into an object beam and a reference beam; a second beam splitter disposed in the optical path of the object beam for receiving the object beam and the reference beam penetrating a transparent planar element under test; an objective lens disposed between the first beam splitter and the second beam splitter for collecting the object beam transmitted from the transparent planar element under test and magnifying the image of the transparent planar element under test; at least one polarizing element disposed in the optical path of the second beam splitter for generating superimposed interference of the object beam and the reference beam with orthogonal polarization directions; at least one image sensor disposed in the optical path of at least one polarizing element for recording the interference pattern of the orthogonal polarization directions; and a processing unit coupled to at least one image sensor for performing numerical reconstruction and data analysis on the recorded interference pattern.

[0009] In one embodiment, the first beam splitter is a polarized beam splitter or a non-polarized beam splitter, and the beam is a coherent beam.

Implementation Method

[0014] This invention will be described in detail here with reference to specific embodiments and their viewpoints. Such descriptions are for illustrative purposes only and are not intended to limit the scope of the invention. Therefore, in addition to the specific and preferred embodiments described in the specification, the invention can also be widely implemented in other different embodiments. The following describes the implementation of the invention through specific embodiments. Those skilled in the art can easily understand the effectiveness and advantages of the invention from the content disclosed in this specification. Furthermore, the invention can also be used and implemented through other specific embodiments, and the various details set forth in this specification can be applied based on different needs, and various modifications or changes can be made without departing from the spirit of the invention.

[0015] This invention discloses a novel method and apparatus for full-vector field detection of transparent planar elements, which is particularly suitable for the detection of full-field wavefront and polarization characteristics of planar elements with micro-nano structures, such as metalens and through glass vias (TGVs).

[0016] This invention overcomes the limitations of existing Shack-Hartmann wavefront sensors and traditional interferometers in detecting miniaturized, discontinuous step wavefronts, achieving high-resolution, full-field detection of the amplitude, phase, and polarization state of transmitted light waves from planar optical elements. The method of this invention is based on digital holography, recording two sets of digital holograms with orthogonal polarization directions and utilizing numerical reconstruction techniques to simultaneously acquire the amplitude and phase distribution and polarization information of the transmitted light waves from the planar optical element under test. This method not only enables precise measurement of the wavefront phase distribution of planar optical elements with micro / nano structures but also simultaneously acquires their polarization modulation characteristics, providing comprehensive and accurate quantitative data for the design optimization, process improvement, and performance evaluation of planar optical elements.

[0017] The apparatus of the present invention includes a digital holographic microscope system, which comprises a light source, a first beam splitter, an objective lens, a second beam splitter, at least one orthogonal polarization generating element or wave plate element, and at least one image sensor. With this configuration, interference patterns of two orthogonal polarization directions can be recorded simultaneously, thereby enabling the detection of the full-vector field of a planar optical element with a micro / nano structure.

[0018] Embodiments of the present invention employ a digital holographic microscope system, which may include off-axis, coaxial, and common-path interference structures. Holographic recording methods for interference patterns with two orthogonal polarization directions include single-port (using a single polarization element to rotate in orthogonal polarization directions) digital holographic microscope systems and dual-port (using two polarization elements to detect orthogonal polarization directions) digital holographic microscope systems.

[0019] Figure 1 is a schematic diagram of the architecture of a single-port digital holographic microscope system according to an embodiment of the present invention. In this embodiment, the single-port digital holographic microscope system includes: a light source 100 for generating a light beam 101, such as a coherent light beam. The light source 100 can be a laser for providing a light beam with polarization characteristics. It should be noted that the light beam 101 generated by the laser is not limited by the wavelength of the light source (for example, the wavelength can be 635 nm). This laser can include, for example, gas lasers such as helium-neon lasers, carbon dioxide lasers, etc., or solid lasers such as ruby ​​lasers, titanium-sapphire lasers, or laser diodes, etc., but is not limited to these; a spatial filter 102 for removing noise from the light beam 101. The noise-removed light beam 101 is collimated by a first lens L1; a first beam splitter 106 can be a polarized beam splitter (PBS) or a non-polarized beam splitter (PBS). A beam splitter (BS) is used to split an input beam (e.g., the coherent beam described above) 101 into an object beam 105 and a reference beam 103. The split object beam 105 has its direction of travel changed by a second mirror M2. After passing through a transparent planar element 130, the object beam 105 passes through an objective lens 108, a second lens L2, and a second beam splitter 110 to reach an image sensor 112. The split reference beam 103 has its direction of travel changed by a third mirror M3, and the optical path difference is controlled. The reference beam 103 then has its direction changed by the second beam splitter 110 to reach the image sensor 112. The objective lens 108 is used to collect the object beam 105 transmitted from the transparent planar element 130 and to magnify the image of the transparent planar element 130. It should be noted that the objective lens described herein includes an objective lens with an unlimited numerical aperture (NA) value, depending on the lateral resolution and field of view required for imaging the transparent planar element 130.

[0020] In one embodiment of the single-port digital holographic microscope system disclosed in this invention, referring to FIG1, the first beam splitter 106 is a polarized beam splitter (PBS) used to split the input beam (e.g., the coherent beam described above) 101 into an object beam 105 and a reference beam 103, wherein the object beam 105 has a first polarization (horizontal polarization or P-polarization) and the reference beam 103 has a second polarization (vertical polarization or S-polarization), that is, the object beam 105 and the reference beam 103 are linearly polarized light and orthogonal to each other. Referring to FIG1, the noise-removed beam 101 is collimated by the first lens L1, and the direction of travel of the beam 101 is changed by the first mirror M1. In this embodiment, the direction of travel of the beam 101 is rotated by 90 degrees due to the configuration of the first mirror M1. The aforementioned single-port digital holographic microscope system further includes a first wave plate element 114, wherein the first wave plate element 114 is a half-wave plate, disposed between the first mirror M1 and the first beam splitter 106, for adjusting the beam splitting ratio of the object beam 105 and the reference beam 103; and a second wave plate element 116, wherein the second wave plate element 116 is a half-wave plate, disposed between the first beam splitter 106 and the third mirror M3, for adjusting the polarization state of the reference beam 103. For example, by rotating the second wave plate element 116 by 45 degrees, the reference beam 103 can be rotated 90 degrees from the second polarization (vertical polarization) to the first polarization (horizontal polarization). Therefore, the reference beam 103 after being rotated by the second wave plate element 116 and the object beam 105 that has passed through the transparent plane element 130 and the objective lens 108 have the same polarization state. After the two beams are collected by the second beam splitter 110, they can generate superimposed interference of the object beam 105 and the reference beam 103. A polarization element 120 is disposed between the second beam splitter 110 and the image sensor 112. The polarization element 120 is a rotatable linear polarizer or waveplate element, used to generate superimposed interference of an object beam 105 and a reference beam 103 with orthogonal polarization directions (i.e., horizontal and vertical polarization directions). The image sensor 112 is used to record interference patterns in the horizontal and vertical polarization directions respectively. A processing unit electrically coupled to the image sensor 112 is disposed in a digital computer (not shown) for numerical reconstruction and data analysis of the recorded interference patterns. The image sensor 112 collects the reference beam 103 and the object beam 105, and records the digital holographic interference fringes formed by the object beam 105 and the reference beam 103 diffracted by the transparent planar element 130, including the horizontal and vertical polarization directions. The digital holographic interference fringes can be converted into digital signals by the image sensor 120.The image sensor 112 discussed herein may be, for example, a charge-coupled device (CCD) or a complementary metal-oxide-semiconductor (CMOS), but is not limited thereto; the appropriate image sensor 112 should be used according to actual needs. A digital computer, electrically coupled to the image sensor 112, is used to reconstruct the wavefront information of the transparent planar element 130, and can perform quantization analysis on this wavefront information to obtain complete amplitude, phase, and polarization state modulation characteristics. The digital computer discussed herein includes a computer-readable medium containing computer program code, and can be executed by a computer processor of any or all steps, operations, or described programs.

[0021] In another embodiment of the single-port digital holographic microscope system disclosed in this invention, referring to FIG1, the first beam splitter 106 is a polarized beam splitter (PBS) used to split the input beam (e.g., the coherent beam described above) 101 into an object beam 105 and a reference beam 103, wherein the object beam 105 has a first polarization (horizontal polarization or P-polarization) and the reference beam 103 has a second polarization (vertical polarization or S-polarization), that is, the object beam 105 and the reference beam 103 are each linearly polarized light and are orthogonal to each other. Referring to FIG1, the noise-removed beam 101 is collimated by the first lens L1, and the direction of travel of the beam 101 is changed by the first mirror M1. In this embodiment, the direction of travel of the beam 101 is rotated by 90 degrees due to the configuration of the first mirror M1. The aforementioned single-port digital holographic microscope system further includes a first waveplate element 114, wherein the first waveplate element 114 is a half-wave plate, disposed between the first mirror M1 and the first beam splitter 106, for adjusting the beam splitting ratio of the object beam 105 and the reference beam 103; and a second waveplate element 116, wherein the second waveplate element 116 is a quarter-wave plate, disposed between the first beam splitter 106 and the third mirror M3, for adjusting the polarization state of the reference beam 103, so that the reference beam 103 after passing through the second waveplate element 116 is circularly polarized light; therefore, the reference beam 103 (circularly polarized light) passing through the second waveplate element 116 and the object beam 105 (horizontally polarized light) passing through the transparent plane element 130 and the objective lens 108 can generate superimposed interference of the object beam 105 and the reference beam 103 after being collected by the second beam splitter 110. A polarization element 120 is disposed between the second beam splitter 110 and the image sensor 112. The polarization element 120 is a rotatable linear polarizer or waveplate element, used to generate superimposed interference of an object beam 105 and a reference beam 103 with orthogonal polarization directions (i.e., horizontal and vertical polarization directions). The image sensor 112 is used to record interference patterns in the horizontal and vertical polarization directions respectively. A processing unit electrically coupled to the image sensor 112 is disposed in a digital computer (not shown) for numerical reconstruction and data analysis of the recorded interference patterns. The image sensor 112 collects the reference beam 103 and the object beam 105, and records the digital holographic interference fringes formed by the object beam 105 and the reference beam 103 diffracted by the transparent planar element 130, including the horizontal and vertical polarization directions. The digital holographic interference fringes can be converted into digital signals by the image sensor 120.The image sensor 112 discussed herein can be, for example, a charge-coupled device (CCD) or a complementary metal-oxide-semiconductor (CMOS), but is not limited thereto. The appropriate image sensor 112 should be used based on actual needs. The connection relationship between the image sensor 112 and the digital computer, as well as the numerical analysis operation, are the same as described above and will not be repeated here.

[0022] In another embodiment of the single-port digital holographic microscope system disclosed in this invention, referring to FIG1, the first beam splitter 106 is a non-polarized beam splitter (BS). Similar to the aforementioned example of the single-port digital holographic microscope system, the noise-removed beam 101 passes through the first lens L1 to generate a collimated beam, and the direction of travel of the beam 101 is changed by the first mirror M1. In this embodiment, the direction of travel of the beam 101 is rotated by 90 degrees due to the configuration of the first mirror M1. The aforementioned single-port digital holographic microscope system further includes a first wave plate element 114, wherein the first wave plate element 114 is a quarter-wave plate, disposed between the first mirror M1 and the first beam splitter 106, so that the beam 101 after passing through the first wave plate element 114 is circularly polarized light; in this embodiment, the second wave plate element 116 can be omitted. The circularly polarized light passing through the first wave plate element 114 is split into an object beam 105 and a reference beam 103 with circular polarization characteristics by the first beam splitter 106. Therefore, both the reference beam 103 and the object beam 105 passing through the transparent plane element 130 and the objective lens 108 are circularly polarized light. After being collected by the second beam splitter 110, the object beam 105 and the reference beam 103 can be superimposed and interfered. The polarization element 120 is disposed between the second beam splitter 110 and the image sensor 112. The polarization element 120 is a rotatable linear polarizer or wave plate element, used to generate superimposed interference of the object beam 105 and the reference beam 103 with orthogonal polarization directions (i.e., horizontal and vertical polarization directions) through the rotating polarization element 120. The aforementioned image sensor 112 is used to record interference patterns in the horizontal and vertical polarization directions, respectively. A processing unit electrically coupled to the image sensor 112 and disposed in a digital computer (not shown) is used to perform numerical reconstruction and data analysis on the recorded interference patterns. Specifically, the image sensor 112 collects the reference beam 103 and the object beam 105, and records the digital holographic interference fringes formed by the object beam 105 and the reference beam 103, which are diffracted by the transparent planar element 130, including the horizontal and vertical polarization directions. The digital holographic interference fringes can be converted into digital signals by the image sensor 120. The connection relationship between the image sensor 112 and the digital computer, and the numerical analysis operation discussed here, are the same as described above and will not be repeated here.

[0023] Figure 2 is a schematic diagram of the architecture of a dual-port digital holographic microscope system according to an embodiment of the present invention. In this embodiment, the dual-port digital holographic microscope system includes: a light source 100 for generating a light beam 101, such as a coherent light beam. The light source 100 can be a laser for providing a light beam with polarization characteristics. It should be noted that the light beam 101 generated by the laser is not limited by the wavelength of the light source (for example, the wavelength can be 635 nm). This laser can include, for example, gas lasers such as helium-neon lasers, carbon dioxide lasers, etc., or solid lasers such as ruby ​​lasers, titanium-sapphire lasers, or laser diodes, etc., but is not limited to these; a spatial filter 102 for removing noise from the light beam 101. The noise-removed light beam 101 is collimated by a first lens L1; and a first beam splitter 106 can be a polarized beam splitter. A PBS (Polypolarized Beam Splitter) or a nonpolarized beam splitter is used to split the input beam (e.g., the coherent beam mentioned above) 101 into an object beam 105 and a reference beam 103. The split object beam 105 changes its direction of travel through a second mirror M2. After passing through a transparent planar element 130, the object beam 105 passes through an objective lens 108 and a second lens L2, and can then pass through a second beam splitter 110 to reach a first image sensor 112a or change its direction through the second beam splitter 110 to reach a second image sensor 112b. The split reference beam 103 changes its direction of travel and controls the optical path difference through a third mirror M3. The reference beam 103 then changes its direction through the second beam splitter 110 to reach a first image sensor 112a or passes through the second beam splitter 110 to reach a second image sensor 112b. The objective lens 108 is used to collect the object beam transmitted from the transparent planar element 130 and to magnify the image of the transparent planar element 130. It should be noted that the objectives described herein include those with no limitation on numerical aperture (NA) values, depending on the lateral resolution and field of view required for imaging the aforementioned transparent planar element 130.

[0024] In one embodiment of the dual-port digital holographic microscope system disclosed in this invention, referring to FIG2, the first beam splitter 106 is a polarized beam splitter (PBS) used to split the input beam (e.g., the coherent beam described above) 101 into an object beam 105 and a reference beam 103, wherein the object beam 105 has a first polarization (horizontal polarization or P-polarization) and the reference beam 103 has a second polarization (vertical polarization or S-polarization), that is, the object beam 105 and the reference beam 103 are linearly polarized light and orthogonal to each other. Referring to FIG2, the noise-removed beam 101 is collimated by the first lens L1, and the direction of travel of the beam 101 is changed by the first mirror M1. In this embodiment, the direction of travel of the beam 101 is rotated by 90 degrees due to the configuration of the first mirror M1. The aforementioned dual-port digital holographic microscope system further includes a first waveplate element 114, wherein the first waveplate element 114 is a half-wave plate, disposed between the first mirror M1 and the first beam splitter 106, for adjusting the beam splitting ratio of the object beam 105 and the reference beam 103; and a second waveplate element 116, wherein the second waveplate element 116 is a quarter-wave plate, disposed between the first beam splitter 106 and the third mirror M3, for adjusting the polarization state of the reference beam 103, such that the reference beam 103 after passing through the second waveplate element 116... 3 represents circularly polarized light; therefore, the reference beam 103 (circularly polarized light) passing through the second wave plate element 116 and the object beam 105 (horizontally polarized light) passing through the transparent plane element 130 and the objective lens 108, and the superimposed beams collected by the second beam splitter 110 in the first and second directions, can simultaneously generate superimposed interference between the object beam 105 and the reference beam 103; wherein the first direction is the direction in which the object beam 105 penetrates the second beam splitter 110, and the second direction is the direction in which the reference beam 103 penetrates the second beam splitter 110. In this embodiment, a first polarization element 120a and a first image sensor 112a are disposed in a first direction, wherein the first polarization element 120a is disposed between the second beam splitter 110 and the first image sensor 112a, and its polarization detection direction is set to the first polarization direction (e.g., the horizontal polarization direction) so that the superposition interference of the object beam 105 and the reference beam 103 in the first polarization direction is recorded in the first image sensor 112a disposed in the direction; a second polarization element 120b and a second image sensor 112b are disposed in a second direction, wherein the second polarization element 120b is disposed between the second beam splitter 110 and the second image sensor 112b, and its polarization detection direction is set to the second polarization direction (e.g., the vertical polarization direction) so that the superposition interference of the object beam 105 and the reference beam 103 in the second polarization direction is recorded in the second image sensor 112b disposed in the direction.Therefore, in the dual-port digital holographic microscope system shown in Figure 2, the two image sensors (first image sensor 112a and second image sensor 112b) can simultaneously record interference patterns in the horizontal and vertical polarization directions. A processing unit electrically coupled to the first image sensor 112a and the second image sensor 112b is located in a digital computer (not shown) for numerical reconstruction and data analysis of the recorded interference patterns. The first image sensor 112a and the second image sensor 112b collect the reference beam 103 and the object beam 105 to record the digital holographic interference fringes formed by the object beam 105 and the reference beam 103 diffracted by the transparent planar element 130. The digital holographic interference fringes can be converted into digital signals by the first image sensor 112a and the second image sensor 112b. The first image sensor 112a and the second image sensor 112b discussed herein can be, for example, a charge-coupled device (CCD) or a complementary metal-oxide-semiconductor (CMOS), but are not limited thereto. The appropriate first image sensor 112a and second image sensor 112b should be used based on actual needs. A digital computer, electrically coupled to the first image sensor 112a and the second image sensor 112b, is used to reconstruct the wavefront information of the transparent planar element 130. This wavefront information can be quantized and analyzed to obtain complete amplitude, phase, and polarization state modulation characteristics. The digital computer discussed herein includes a computer-readable medium containing computer program code and can be executed by a computer processor of any or all steps, operations, or described programs.

[0025] In another embodiment of the dual-port digital holographic microscope system disclosed in this invention, referring to FIG2, the first beam splitter 106 is a non-polarized beam splitter, similar to the aforementioned example of the dual-port digital holographic microscope system. The noise-removed beam 101 passes through the first lens L1 to generate a collimated beam, and the direction of travel of the beam 101 is changed by the first mirror M1. In this embodiment, the direction of travel of the beam 101 is rotated by 90 degrees due to the configuration of the first mirror M1. The aforementioned dual-port digital holographic microscope system further includes a first wave plate element 114, wherein the first wave plate element 114 is a quarter-wave plate, disposed between the first mirror M1 and the first beam splitter 106, so that the beam 101 after passing through the first wave plate element 114 is circularly polarized light; in this embodiment, the second wave plate element 116 can be omitted. The circularly polarized light passing through the first wave plate element 114 is split into an object beam 105 and a reference beam 103 with circular polarization characteristics by the first beam splitter 106. Therefore, both the reference beam 103 and the object beam 105 passing through the transparent plane element 130 and the objective lens 108 are circularly polarized light. The superimposed beams in the first and second directions collected by the second beam splitter 110 can simultaneously generate superimposed interference of the object beam 105 and the reference beam 103. The first direction is the direction in which the object beam 105 passes through the second beam splitter 110, and the second direction is the direction in which the reference beam 103 passes through the second beam splitter 110. In this embodiment, a first polarization element 120a and a first image sensor 112a are disposed in a first direction, wherein the first polarization element 120a is disposed between the second beam splitter 110 and the first image sensor 112a, and its polarization detection direction is set to the first polarization direction (e.g., the horizontal polarization direction) so that the superposition interference of the object beam 105 and the reference beam 103 in the first polarization direction is recorded in the first image sensor 112a disposed in the direction; a second polarization element 120b and a second image sensor 112b are disposed in a second direction, wherein the second polarization element 120b is disposed between the second beam splitter 110 and the second image sensor 112b, and its polarization detection direction is set to the second polarization direction (e.g., the vertical polarization direction) so that the superposition interference of the object beam 105 and the reference beam 103 in the second polarization direction is recorded in the second image sensor 112b disposed in the direction. Therefore, the two image sensors (first image sensor 112a and second image sensor 112b) in the dual-port digital holographic microscope system shown in Figure 2 can simultaneously record interference patterns in the horizontal and vertical polarization directions; a processing unit electrically coupled to the first image sensor 112a and the second image sensor 112b is set in a digital computer (not shown) for numerical reconstruction and data analysis of the recorded interference patterns.The first image sensor 112a and the second image sensor 112b collect the reference beam 103 and the object beam 105, and record the digital holographic interference fringes formed by the object beam 105 and the reference beam 103 diffracted by the transparent planar element 130. These digital holographic interference fringes can be converted into digital signals by the first image sensor 112a and the second image sensor 112b. The first image sensor 112a and the second image sensor 112b collect the reference beam 103 and the object beam 105, and record the digital holographic interference fringes formed by the object beam 105 and the reference beam 103 diffracted by the transparent planar element 130, including horizontal and vertical polarization directions. These digital holographic interference fringes can be converted into digital signals by the first image sensor 112a and the second image sensor 112b. The connection and numerical analysis operation of the first image sensor 112a and the second image sensor 112b with the digital computer discussed here are the same as described above and will not be repeated here.

[0026] The following paragraphs describe how to perform data acquisition and computation, numerical reconstruction and numerical analysis using the digital holographic microscopy inspection system disclosed in Figure 1 or Figure 2: (1) Data acquisition and computation: Referring to Figure 1, adjust the optical path difference of the reference beam 103 so that the two beams of light, the reference beam 103 and the object beam 105, form a holographic pattern on the image sensor 112. At the same time, record the interference patterns of two orthogonal polarization directions. The number of pixels of the image sensor 112 is 1024×1024, and the pixel size is 5.2μm. (2) Numerical reconstruction: The recorded digital hologram is numerically reconstructed using the Fresnel diffraction approximation method. The reconstruction process includes: (a) performing a Fast Fourier Transform (FFT) on the original hologram; (b) applying a Spatial Filter (SF) in the frequency domain to remove zero-order terms and conjugate images; and (c) performing an Inverse Fast Fourier Transform (IFFT) to obtain the complex field distribution. (3) Data analysis: The specific steps include: (a) extracting amplitude and phase information from the reconstructed complex field; (b) obtaining a continuous phase distribution using a phase expansion algorithm; and (c) calculating the polarization state of the orthogonal hologram reconstruction in the following manner. Here, the polarization state of the transmitted light wave of the sample can be represented by the Jones vector method as follows: [Mathematical Formula 1] where Ax and Ay are the light wave amplitudes in two orthogonal directions (i.e., horizontal and vertical polarization directions), Φx and Φy are the light wave phases in two orthogonal directions, and Φo is the constant phase contained in the object beam 105. Meanwhile, the polarization state of the light wave transmitted through the sample (e.g., transparent planar element 130) can correspond to the polarization ellipse shown in Figure 3, and its relationship can be derived as follows: [Mathematical Equation 2] From the relationship between Equation (2) and Figure 3, it can be seen that the polarization state of the light wave transmitted through the sample (e.g., transparent planar element 130) is related to the amplitude (Ax, Ay) and phase (Φx, Φy) of the light wave on the x-axis and y-axis of its Jones vector field. Wherein, φ is the azimuth angle of the polarized light and θ is the ellipticity angle. Therefore, as long as the amplitude (Ax, Ay) and phase (Φx, Φy) of the light wave transmitted through the sample (e.g., transparent planar element 130) are measured simultaneously, the polarization state of the light wave transmitted through the sample can be obtained according to the relationship of Equation (2) and the schematic diagram of the light wave polarization ellipse in Figure 3. Because digital holography can simultaneously reconstruct the full-field wavefront amplitude (Ax, Ay) and phase (Φx, Φy) images of the transmitted wave of the sample.Next, in step (d), the obtained full-field wavefront phase distribution is used to calculate the wavefront aberration function and the Strehl ratio to evaluate the imaging quality of the transparent planar element 130 (refer to Figures 1-2).

[0027] In one embodiment, in addition to the Fresnel diffraction approximation method and Fourier transform method mentioned above, the numerical reconstruction method may also include the decomposition method, angular spectrum method, etc.

[0028] In one embodiment, the transparent planar element 130 described above may include micro-nano structures such as super-lenses and glass substrate guide holes, or combinations thereof.

[0029] Figure 4 is a flowchart illustrating the steps of a method for detecting the full-field vector characteristics of a transparent planar element according to an embodiment of the present invention. In this embodiment, a method for detecting the full-field wavefront and polarization characteristics of a transparent planar element 130 (refer to Figures 1-2) using a digital holographic microscopy detection system disclosed in Figure 1 or Figure 2 includes the following steps: In step S401, a digital holographic microscopy detection system (refer to Figures 1-2) is provided, which includes at least a light source 100, a first beam splitter 106, an objective lens 108, a second beam splitter 110, at least one rotatable polarizing element (e.g., 120, 120a, 120b) and at least one image sensor (e.g., 112, 112a, 112b); In step S402, the light beam 101 generated by the light source 100 in the above-mentioned digital holographic microscopy detection system is split into an object beam 105 and a reference beam 103 by the first beam splitter 106; In step S403, the object beam 105... After penetrating the transparent planar element 130 under test, the light beam, together with the reference beam 103, penetrates at least one rotatable polarizing element (e.g., 120, 120a, 120b), generating two sets of interference patterns with orthogonal polarization directions on at least one image sensor (e.g., 112, 112a, 112b). In step S404, the interference patterns with the two sets of orthogonal polarization directions are recorded as a digital hologram via the at least one image sensor (e.g., 112, 112a, 112b). In step S405, the digital hologram is numerically reconstructed by a digital computer to obtain the amplitude and phase information of the transmitted light wave in the two orthogonal polarization directions of the transparent planar element 130 under test. In step S406, the digital computer calculates the full-field wavefront amplitude, phase distribution, and polarization state of the transparent planar element under test based on the obtained amplitude and phase information.

[0030] In one embodiment, referring to Figures 1-2, the first beam splitter 106 is a polarized beam splitter or a non-polarized beam splitter, used to split the beam 101 into an object beam 105 and a reference beam 103. The objective lens 130 is disposed in the optical path of the object beam 105 and located between the first beam splitter 106 and the second beam splitter 110, used to collect the object beam transmitted from the transparent planar element 130 under test and to magnify the image of the transparent planar element 130 under test. The second beam splitter 110 is a non-polarized beam splitter, disposed between the objective lens 108 and at least one image sensor (e.g., 112, 112a, 112b), used to receive the object beam 105 and the reference beam 103 that penetrate the transparent planar element 130 under test. At least one of the aforementioned rotatable polarizing elements (e.g., 120, 120a, 120b) is disposed between the second beam splitter 110 and at least one image sensor (e.g., 112, 112a, 112b) to generate superposition interference between the object beam 105 and the reference beam 103 with orthogonal polarization directions.

[0031] The advantages of the present invention as described above include: (1) achieving full-field, high-resolution detection of transmitted light waves from planar optical elements with micro-nano structures, overcoming the limitations of the prior art; (2) simultaneously acquiring amplitude, phase, and polarization information, providing comprehensive optical characteristic characterization; (3) eliminating the need for complex collimating optical systems or imaging systems, reducing measurement errors; (4) providing a fast detection process, applicable to real-time characterization and quality control of planar optical elements with micro-nano structures; and (5) providing quantitative performance evaluation indicators, such as wavefront aberration function and Strehl ratio (SR), which helps optimize the performance of planar optical elements.

[0032] The above description is a preferred embodiment of the present invention. Those skilled in the art should understand that it is used to illustrate the present invention and not to limit the scope of the patent rights claimed by the present invention. The scope of patent protection shall be determined by the appended claims and their equivalent fields. Any modifications or refinements made by those skilled in the art without departing from the spirit or scope of this patent are equivalent changes or designs made under the spirit disclosed in the present invention and should be included in the scope of the following claims. [Simplified Explanation of the Diagram]

[0010] [Figure 1] shows a schematic diagram of the architecture of a single-port digital holographic microscope system according to one embodiment of the present invention.

[0011] [Figure 2] shows a schematic diagram of the architecture of a dual-port digital holographic microscope system according to one embodiment of the present invention.

[0012] [Figure 3] shows a schematic diagram of the optical wave polarization ellipse corresponding to an embodiment of the present invention.

[0013] [Figure 4] shows a flowchart illustrating the steps of a method for detecting the full vector field of a transparent planar element according to an embodiment of the present invention.

Claims

1. A method for detecting the omnidirectional field of a transparent planar element, comprising: providing a digital holographic microscope system, including at least a light source, a first beam splitter, an objective lens, a second beam splitter, at least one rotatable polarizing element, and at least one image sensor; splitting a light beam generated by the light source into an object beam and a reference beam by the first beam splitter, wherein the first beam splitter is a polarized beam splitter or a non-polarized beam splitter; when the first beam splitter is a non-polarized beam splitter, the digital holographic system further includes a first waveplate element as a quarter-wave plate, disposed between the light source and the first beam splitter, for adjusting the polarization state of the reference beam and the object beam; When the first beam splitter is the polarized beam splitter, the digital holographic system further includes: using the first waveplate element as a half-wave plate, disposed between the light source and the first beam splitter to adjust the beam splitting ratio of the object beam and the reference beam; and using a second waveplate element as a quarter-wave plate, disposed on the path of the reference beam to adjust the polarization state of the reference beam; guiding the object beam through a transparent planar element under test; guiding the object beam and the reference beam through at least one rotatable polarizing element to generate two sets of interference patterns with orthogonal polarization directions on at least one image sensor; recording the interference patterns with the two sets of orthogonal polarization directions as a digital hologram using the at least one image sensor; performing numerical reconstruction on the digital hologram using a digital computer to obtain the amplitude and phase information of the transmitted light wave of the transparent planar element under test in the two orthogonal polarization directions; and calculating the full-field wavefront amplitude, phase distribution, and polarization state of the transparent planar element under test using the obtained amplitude and phase information by the digital computer. The digital computer calculates the wavefront aberration function and the Strehl ratio based on the obtained full-field wavefront phase distribution to evaluate the imaging quality of the transparent planar element under test; and the transparent planar element under test includes a super-lens, a glass substrate aperture, or a combination thereof.

2. The method for detecting the full vector field of a transparent planar element as described in claim 1, wherein the numerical reconstruction method includes the Fresnel diffraction approximation, Fourier transform, decomposition, or angular spectrum method.

3. The method for full-vector field detection of a transparent planar element as described in claim 1, wherein the at least one rotatable polarizing element can be replaced by a waveplate element.

4. The method for full-vector field detection of a transparent planar element as described in claim 3, wherein the objective lens is disposed in the optical path of the object beam and located between the first beam splitter and the second beam splitter, for collecting the object beam transmitted from the transparent planar element under test and magnifying the image of the transparent planar element under test.

5. The method for full-vector field detection of a transparent planar element as described in claim 4, wherein the second beam splitter is a non-polarized beam splitter disposed between the objective lens and the at least one image sensor, for receiving the object beam penetrating the transparent planar element under test and the reference beam.

6. The method for full-vector field detection of a transparent planar element as described in claim 5, wherein the at least one rotatable polarizing element is disposed between the second beam splitter and the at least one image sensor for generating superimposed interference of the object beam and the reference beam with orthogonal polarization directions.

7. A device for detecting the total vector field of a transparent planar element, comprising: A light source for generating a light beam; a first beam splitter for splitting the light beam into an object beam and a reference beam, wherein the first beam splitter is a polarized beam splitter or a non-polarized beam splitter; when the first beam splitter is a non-polarized beam splitter, the digital holographic system further includes a first waveplate element, as a quarter-wave plate, disposed between the light source and the first beam splitter, for adjusting the polarization state of the reference beam and the object beam; when the first beam splitter is a polarized beam splitter, the digital holographic system further includes utilizing the first waveplate element, as a half-wave plate, disposed between the light source and the first beam splitter, for adjusting the beam splitting ratio of the object beam and the reference beam, and utilizing a second waveplate element, as a quarter-wave plate, disposed on the path of the reference beam, for adjusting the polarization state of the reference beam; a second beam splitter, disposed in the optical path of the object beam, for receiving the object beam and the reference beam that have penetrated a transparent planar element under test; An objective lens, disposed between the first beam splitter and the second beam splitter, is used to collect the object beam transmitted through the transparent planar element under test and to magnify the image of the transparent planar element under test; at least one polarizing element, disposed in the optical path of the second beam splitter, is used to generate beam superposition interference between the object beam and the reference light in orthogonal polarization directions; at least one image sensor, disposed in the optical path of the at least one polarizing element, is used to record the interference pattern in the orthogonal polarization directions; and a processing unit, coupled to the at least one image sensor, is used to perform numerical reconstruction on the recorded interference pattern to obtain the amplitude and phase information of the transmitted light wave of the transparent planar element under test, and to calculate the wavefront aberration function and Strehl ratio based on the phase information to evaluate the imaging quality of the transparent planar element under test, wherein the transparent planar element under test includes a superlens, a glass substrate aperture, or a combination thereof.

8. The apparatus for detecting the full vector field of a transparent planar element as described in claim 7, wherein the light beam is a coherent light beam.

9. The apparatus for full-vector field detection of a transparent planar element as claimed in claim 7, wherein the at least one polarizing element is a rotatable polarizing element disposed between the second beam splitter and the at least one image sensor, for generating superposition interference of the object beam and the reference beam with orthogonal polarization directions.

Images