Fp-based channel dispersion type polarization spectrometer and polarization spectrum measurement method thereof

Abstract

The present application belongs to the technical field of optical metrology testing, and particularly relates to a channel dispersion type polarization spectrometer based on FP and a polarization spectrum measurement method thereof. The system comprises, in sequence along the light path direction, a telescope objective, a polarization modulation module, a magnifying lens, a Fabry-Perot etalon, an optical imaging lens and a detector. The telescope objective acquires parallel light and makes the parallel light incident to the polarization modulation module. The polarization modulation module generates a modulation spectrum curve and modulates the polarization spectrum data of the parallel light to obtain a modulation light beam. The magnifying lens adjusts the modulation light beam, and the adjusted modulation light beam is incident to the Fabry-Perot etalon. The Fabry-Perot etalon performs spectral dispersion processing on the modulation light beam to obtain a dispersed light beam. The optical imaging lens makes the dispersed light beam image on the detector. The detector receives the dispersed light beam to obtain a modulated polarization spectrum curve. The present application does not have the case of spectral line bending under the condition of high transmittance.

Description

Technical Field

[0001] This invention belongs to the field of optical metrology and testing technology, and particularly relates to a channel dispersive polarization spectrometer based on FP (Fabry-Polo) and its polarization spectrum measurement method. Background Technology

[0002] With the development of technology, the demand for remote sensing data has expanded beyond simply qualitatively or semi-quantitatively describing the basic characteristics of ground targets. This places higher demands on space optical remote sensors, enabling them to quantitatively interpret geophysical parameters. In the field of polarization optical remote sensing, Channeled Dispersive Imaging Spectropolarimetry (CDISP), as an advanced polarization spectral measurement technique, combines an intensity modulation module with a dispersive spectrometer to simultaneously acquire polarization and spectral information. Currently, using gratings as dispersive elements in CDISP suffers from low diffraction efficiency and high stray light; using dispersive prisms as dispersive elements presents the problem of spectral line bending. Therefore, employing other spectral dispersive elements and combining them with CDISP imaging technology to detect both polarization and spectral information, while avoiding the problems associated with gratings and prisms as dispersive elements, is a crucial technical challenge that researchers in this field urgently need to address. Summary of the Invention

[0003] In view of this, the present invention aims to provide a Fabry-Poirot-based FP-based channel dispersive polarization spectrometer and its polarization spectral measurement method to solve the problems of using gratings and prisms as dispersive elements in channel dispersive polarization spectrometers. The present invention does not have spectral line bending under high transmittance conditions, thus avoiding the problems caused by grating dispersion and prism dispersion as dispersive elements in channel dispersive polarization spectrometers.

[0004] To achieve the above objectives, the technical solution created by this invention is implemented as follows: A channel-dispersive polarization spectrometer based on photonics (FP) includes a telescope objective, a polarization modulation module, a magnifying lens, a Fabry-Poirot etalon, an optical imaging lens, and a detector arranged sequentially along the optical path. The telescope objective acquires parallel light and directs it onto the polarization modulation module. The polarization modulation module generates a modulation spectral curve and modulates the polarization spectral data of the parallel light to obtain a modulated beam. The magnifying lens adjusts the modulated beam so that the adjusted modulated beam is directed onto the Fabry-Poirot etalon. The Fabry-Poirot etalon performs spectral dispersion processing on the modulated beam to obtain a dispersive beam. The optical imaging lens images the dispersive beam onto the detector. The detector receives the dispersive beam and obtains the polarization spectral curve modulated by the Fabry-Poirot etalon.

[0005] Furthermore, the polarization modulation module includes a first phase retarder, a second phase retarder, and a linear polarizer arranged sequentially along the optical path. The thickness ratio of the first phase retarder to the second phase retarder is 1:2, and the fast axis direction of the first phase retarder is 0°, the fast axis direction of the second phase retarder is 45°, and the angle between the fast axis direction of the linear polarizer and the horizontal plane is 0°.

[0006] Furthermore, the Fabry-Polo etalon includes a first plate and a second plate arranged sequentially along the optical path direction. The first plate and the second plate have the same structure and are arranged in parallel.

[0007] Furthermore, the wedge angle of the first plate is 30′, the side of the first plate near the magnifying lens is coated with an anti-reflection film with a transmittance of 0.99, the other side of the first plate is coated with an anti-reflection film with a reflectance of 0.98, and the material of the first plate is quartz.

[0008] Furthermore, the detector is either a CMOS detector or a CCD detector.

[0009] A polarization spectral measurement method based on a channel dispersive polarization spectrometer (FP) is disclosed, which includes the following steps: S1: Align the channel dispersive polarization spectrometer with the target to be measured. The parallel light reflected by the target to be measured is incident on the polarization modulation module through the telescope objective. The polarization modulation module generates a modulation spectrum curve and modulates the polarization spectrum data of the parallel light to obtain a modulated beam. S2: The different wavelengths of light contained in the modulated beam are magnified and incident on the Fabry-Polo etalon for coherent superposition to obtain a dispersive beam; S3: The detector receives the dispersive beam and obtains the polarization spectrum curve modulated by the Fabry-Poirot etalon. S4: Demodulate the polarization spectrum curve according to the radiometric calibration coefficient of the channel dispersive polarization spectrometer to obtain the modulation spectrum curve generated by the polarization modulation module; perform Fourier transform processing on the modulation spectrum curve to obtain the polarization spectrum data of the target under test.

[0010] Furthermore, in step S1, the expression for the modulated beam is: ; in, To modulate the beam, , , and The Stokes vector of the polarization spectrum of the target under test. The phase delay introduced for the polarization modulation module.

[0011] Furthermore, in step S2, the transmittance expression of the dispersive beam is: ; in, The transmittance of the dispersive beam is denoted as . The thickness of the Fabry-Polo etalon. Let be the wavelength of the dispersive beam. Let be the angle of incidence of the incident light incident on the Fabry-Polo etalon, and F be an intermediate physical quantity for determining the dispersive beam, which has no physical meaning.

[0012] Furthermore, the expression for the intermediate physical quantity F is: ; Where R is the reflectivity of the antireflective coating of the Fabry-Polo etalon.

[0013] Compared with the prior art, the present invention can achieve the following beneficial effects: This invention creates a channel-dispersive polarization spectrometer based on a photoplethysmometer (FP). By using the FP as the spectral dispersive element, it avoids the low energy utilization of grating-dispersive spectrometers and the spectral line bending problems of prism dispersion, thereby improving the energy utilization of the FP-based channel-dispersive polarization spectrometer and reducing the difficulty of subsequent data processing. This invention will play an important role in the structural design of channel-dispersive polarization spectral imagers and has broad engineering application value. Attached Figure Description

[0014] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments and descriptions of the invention are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 A schematic diagram of the structure of the FP-based channel dispersive polarization spectrometer described in the embodiment of the present invention; Figure 2 A schematic diagram of the polarization modulation module described in the embodiment of the present invention; Figure 3 A schematic diagram of the structure of the Fabry-Poirot etalon as described in an embodiment of the present invention; Figure 4 This is a schematic flowchart of the polarization spectral measurement method of the channel dispersive polarization spectrometer based on FP as described in the embodiments of the present invention.

[0015] Explanation of reference numerals in the attached figures: 1. Telescope objective lens; 2. Polarization modulation module; 3. Magnifying lens; 4. Fabry-Porro etalon; 5. Optical imaging lens; 6. Detector; 7. First phase retarder; 8. Second phase retarder; 9. Linear polarizer; 10. First plate; 11. Second plate. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not constitute a limitation thereof.

[0017] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0018] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0019] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0020] The invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0021] like Figure 1As shown, the present invention proposes a channel dispersive polarization spectrometer based on FP, comprising a telescope objective 1, a polarization modulation module 2, a magnifying lens 3, a Fabry-Polo etalon 4, an optical imaging lens 5, and a detector 6 arranged sequentially along the optical path. The telescope objective 1 acquires parallel light and directs the parallel light onto the polarization modulation module 2; the polarization modulation module 2 generates a modulation spectral curve and modulates the polarization spectral data of the parallel light to obtain a modulated beam; the magnifying lens 3 adjusts the modulated beam (so that the modulated beam meets the incident angle requirements of the Fabry-Polo etalon 4), and directs the adjusted modulated beam onto the Fabry-Polo etalon 4; the Fabry-Polo etalon 4 performs spectral dispersion processing on the modulated beam to obtain a dispersive beam; the optical imaging lens 5 images the dispersive beam onto the detector 6; the detector 6 receives the dispersive beam and obtains the polarization spectral curve modulated by the Fabry-Polo etalon 4.

[0022] like Figure 2 As shown, the polarization modulation module 2 includes a first phase delayer 7, a second phase delayer 8, and a linear polarizer 9 arranged sequentially along the optical path. The thickness ratio of the first phase delayer 7 to the second phase delayer 8 is 1:2, and the fast axis direction of the first phase delayer 7 is 0°, the fast axis direction of the second phase delayer 8 is 45°, and the angle between the fast axis direction of the linear polarizer 9 and the horizontal plane is 0°.

[0023] like Figure 3 As shown, the Fabry-Polo etalon 4 includes a first plate 10 and a second plate 11 arranged sequentially along the optical path. The first plate 10 and the second plate 11 have the same structure and are arranged in parallel.

[0024] The wedge angle of the first plate 10 is 30′. The side of the first plate 10 closest to the magnifying lens 3 is coated with an anti-reflection film with a transmittance of 0.99. The other side of the first plate 10 is coated with an anti-reflection film with a reflectance of 0.98. The material of the first plate 10 is quartz.

[0025] Detector 6 is either a CMOS detector or a CCD detector.

[0026] like Figure 4 As shown, the present invention provides a polarization spectral measurement method for a channel dispersive polarization spectrometer based on FP, which is implemented using a channel dispersive polarization spectrometer based on FP, and specifically includes the following steps: S1: Align the channel dispersive polarization spectrometer with the target to be measured. The parallel light reflected by the target to be measured is incident on the polarization modulation module 2 through the telescope objective 1. The polarization modulation module 2 generates a modulation spectrum curve and modulates the polarization spectrum data of the parallel light to obtain a modulated beam. The expression for the modulated beam is: ; in, To modulate the beam, , , and The Stokes vector of the polarization spectrum of the target under test. The phase delay introduced for polarization modulation module 2.

[0027] S2: The different wavelengths of light contained in the modulated beam are incident on the Fabry-Polo etalon 4 through the magnifying lens 3 for coherent superposition, and exit at different angles (only one wavelength of light exits at this angle) to obtain a dispersive beam. The expression for the transmittance of a dispersive beam is: ; in, The transmittance of the dispersive light beam. The thickness of the Fabry-Poirot standard etalon is 4. Let be the wavelength of the dispersive beam. Let F be the incident angle of the incident light incident on the Fabry-Polo etalon 4, and let F be an intermediate physical quantity for obtaining the dispersive beam, which has no physical meaning.

[0028] The expression for the intermediate physical quantity F is: ; Where R is the reflectivity of the antireflective coating of the Fabry-Polo etalon 4.

[0029] S3: Detector 6 receives the dispersive beam and obtains the polarization spectrum curve modulated by Fabry-Polo etalon 4.

[0030] S4: Demodulate the polarization spectrum curve according to the radiometric calibration coefficient of the channel dispersive polarization spectrometer to obtain the modulation spectrum curve generated by polarization modulation module 2; perform Fourier transform processing on the modulation spectrum curve to obtain the polarization spectrum data of the target under test.

[0031] For a channel-dispersive polarization spectrometer based on FP, the light intensity obtained on detector 6 has the following relationship with the input spectrum: In the formula, DN is the number of electrons acquired by detector 6, K is the radiation calibration coefficient, and I is the modulation spectrum curve generated by polarization modulation module 2. After obtaining the modulation spectrum curve, the polarization spectrum data of the target under test is obtained by using the polarization spectrum data restoration method (Fourier transform, filtering, inverse Fourier transform) of polarization modulation module 2 (PSIM).

[0032] This invention proposes a channel dispersive polarization spectrometer based on FP. This structure can be used to restore the polarization spectrum of the target light under test, which can effectively improve the energy utilization of the instrument (channel dispersive polarization spectrometer based on FP) and avoid the problem of spectral line bending.

[0033] It should be understood that the various forms of processes shown above can be used to reorder, add, or delete steps. For example, the steps described in this invention disclosure can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution disclosed in this invention can be achieved, and this is not limited herein.

[0034] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A polarization spectral measurement method based on a channel dispersive polarization spectrometer (FP), characterized by: A channel-dispersive polarization spectrometer based on photonics (FP) includes a telescope objective, a polarization modulation module, a magnifying lens, a Fabry-Poirot etalon, an optical imaging lens, and a detector arranged sequentially along the optical path. The telescope objective acquires parallel light and directs it onto the polarization modulation module. The polarization modulation module generates a modulation spectral curve and modulates the polarization spectral data of the parallel light to obtain a modulated beam. The magnifying lens adjusts the modulated beam to meet the incident angle requirements of the Fabry-Poirot etalon, directing the adjusted modulated beam onto the Fabry-Poirot etalon. The Fabry-Poirot etalon performs spectral dispersion processing on the modulated beam to obtain a dispersive beam. The optical imaging lens images the dispersive beam onto the detector. The detector receives the dispersive beam and obtains the polarization spectral curve modulated by the Fabry-Poirot etalon. The Fabry-Polo etalon includes a first plate and a second plate arranged sequentially along the optical path direction. The first plate and the second plate have the same structure and are arranged in parallel. The wedge angle of the first plate is 30′. The side of the first plate closest to the magnifying lens is coated with an anti-reflection film with a transmittance of 0.

99. The other side of the first plate is coated with an anti-reflection film with a reflectance of 0.

98. The material of the first plate is quartz. The method specifically includes the following steps: S1: Align the channel dispersive polarization spectrometer with the target to be measured. The parallel light reflected by the target to be measured is incident on the polarization modulation module through the telescope objective. The polarization modulation module generates a modulation spectrum curve and modulates the polarization spectrum data of the parallel light to obtain a modulated beam. In step S1, the expression for the modulated beam is: ； in, To modulate the beam, , , and Let be the Stokes vector of the polarization spectrum of the target under test. The phase delay introduced for the polarization modulation module; S2: The different wavelengths of light contained in the modulated beam are incident on the Fabry-Poirot etalon through the magnifying lens and coherently superimposed to obtain a dispersive beam; In step S2, the transmittance expression of the dispersive beam is: ； in, The transmittance of the dispersive beam is denoted as . The thickness of the Fabry-Polo etalon. Let be the wavelength of the dispersive beam. The incident angle is the incident light incident on the Fabry-Polo etalon, and F is an intermediate physical quantity for obtaining the dispersive beam, which has no physical meaning. S3: The detector receives the dispersive beam and obtains a polarization spectrum curve modulated by the Fabry-Poirot etalon; S4: Demodulate the polarization spectral curve according to the radiometric calibration coefficient of the channel dispersive polarization spectrometer to obtain the modulation spectral curve generated by the polarization modulation module; perform Fourier transform processing on the modulation spectral curve to obtain the polarization spectral data of the target under test.

2. The polarization spectral measurement method of the FP-based channel dispersive polarization spectrometer according to claim 1, characterized in that: The polarization modulation module includes a first phase retarder, a second phase retarder, and a linear polarizer arranged sequentially along the optical path. The thickness ratio of the first phase retarder to the second phase retarder is 1:2, the fast axis direction of the first phase retarder is 0°, the fast axis direction of the second phase retarder is 45°, and the angle between the fast axis direction of the linear polarizer and the horizontal plane is 0°.

3. The polarization spectral measurement method of the FP-based channel dispersive polarization spectrometer according to claim 1, characterized in that: The detector is a CMOS detector or a CCD detector.

4. The polarization spectral measurement method of the FP-based channel dispersive polarization spectrometer according to claim 1, characterized in that: The expression for the intermediate physical quantity F is: ； Where R is the reflectivity of the antireflective coating of the Fabry-Polo etalon.

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