Channel dispersion type polarization spectrometer based on FP (Fabry-Perot) and polarization spectrum measurement method thereof

Abstract

The invention belongs to the technical field of optical metrology testing, and particularly relates to an FP-based channel dispersion type polarization spectrometer and a polarization spectrum measurement method thereof. The system comprises a telescope objective, a polarization modulation module, an amplification lens, a Fabry-Perot etalon, an optical imaging lens and a detector which are sequentially arranged in the light path direction, and the telescope objective obtains parallel light and makes the parallel light enter the polarization modulation module; the polarization modulation module generates a modulation spectrum curve and modulates polarization spectrum data of the parallel light to obtain a modulation light beam; the magnifying lens adjusts the modulated light beam, so that the adjusted modulated light beam enters the Fabry-Perot etalon; the Fabry-Perot etalon performs spectral dispersion processing on the modulated light beam to obtain a dispersed light beam; the optical imaging lens enables the dispersion light beam to be imaged on the detector; the detector receives the dispersion light beam to obtain a modulated polarization spectrum curve. According to the invention, the condition of spectral line bending does not exist under the condition of high transmittance.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical metrology and testing, and in particular relates to a channel dispersion polarization spectrometer based on FP (Fabry-Perot) and a polarization spectrum measurement method thereof. Background Art

[0002] With the development of the times, people's demand for remote sensing data is no longer satisfied with qualitatively or semi-quantitatively describing the basic characteristics of ground objects. This puts forward higher requirements for space optical remote sensors, so that they can quantitatively interpret geophysical parameters. In the field of polarization optical remote sensing, the Channeled Dispersive Imaging Spectropolarimetry (CDISP) is an advanced polarization spectrum measurement technology. By combining the intensity modulation module and the dispersion spectrometer, the polarization information and the spectral information can be obtained simultaneously. At present, the grating as the dispersion element of the channel dispersion polarization spectrometer has the problems of low diffraction efficiency and high stray light; the dispersion prism as the dispersion element of the channel dispersion polarization spectrometer has the problem of spectral bending. Therefore, it is a technical problem that researchers in this field need to solve urgently to use other spectral dispersion elements and combine them with the channel dispersion polarization spectrum imaging technology to realize the detection of polarization information and spectral information and avoid the problems of gratings and prisms as dispersion elements. Summary of the invention

[0003] In view of this, the present invention aims to provide a Fabry-Perot based FP channel dispersion polarization spectrometer and a polarization spectrum measurement method thereof, so as to solve the problems existing in using gratings and prisms as dispersion elements of the channel dispersion polarization spectrometer. The present invention does not have spectral line bending under the condition of high transmittance, and avoids the problems caused by grating dispersion and prism dispersion as dispersion elements of the channel dispersion polarization spectrometer.

[0004] To achieve the above object, the technical solution created by the present invention is implemented as follows: A channel dispersion polarization spectrometer based on FP comprises a telescope objective lens, a polarization modulation module, a magnifying lens, a Fabry-Perot etalon, an optical imaging lens and a detector which are sequentially arranged along an optical path direction, wherein the telescope objective lens obtains parallel light and makes the parallel light incident on 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 modulated light beam; the magnifying lens adjusts the modulated light beam and makes the adjusted modulated light beam incident on the Fabry-Perot etalon; the Fabry-Perot etalon performs spectral dispersion processing on the modulated light beam to obtain a dispersed light beam; the optical imaging lens images the dispersed light beam on the detector; the detector receives the dispersed light beam and obtains a polarization spectrum curve modulated by the Fabry-Perot etalon.

[0005] Furthermore, the polarization modulation module includes a first phase retarder, a second phase retarder and a linear polarizer arranged in sequence along the optical path direction, 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-Perot etalon includes a first plate and a second plate which are sequentially arranged along the optical path direction, and 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 close 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 reflectivity of 0.98, and the material of the first plate is quartz.

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

[0009] A polarization spectrum measurement method based on a FP-based channel dispersion polarization spectrometer is implemented using a FP-based channel dispersion polarization spectrometer, and specifically includes the following steps: S1: Aim the channel dispersion polarization spectrometer at the target to be measured, and the parallel light reflected by the target to be measured is incident on the polarization modulation module through the telescope objective lens. The polarization modulation module generates a modulation spectrum curve and modulates the polarization spectrum data of the parallel light to obtain a modulated light beam; S2: The light of different wavelengths contained in the modulated light beam is incident on the Fabry-Perot etalon through the magnifying lens for coherent superposition to obtain a dispersed light beam; S3: The detector receives the dispersed light beam and obtains the polarization spectrum curve modulated by the Fabry-Perot etalon; S4: demodulating the polarization spectrum curve according to the radiation calibration coefficient of the channel dispersion polarization spectrometer to obtain the modulation spectrum curve generated by the polarization modulation module; performing Fourier transform processing on the modulation spectrum curve to obtain the polarization spectrum data of the target to be measured.

[0010] Furthermore, in step S1, the expression of the modulated light beam is: ; in, To modulate the beam, , , and is the Stokes vector of the polarization spectrum of the target to be measured, The amount of phase delay introduced by the polarization modulation module.

[0011] Furthermore, in step S2, the transmittance expression of the dispersed light beam is: ; in, is the transmittance of the dispersed beam, is the thickness of the Fabry-Perot etalon, is the wavelength of the dispersed beam, is the incident angle of the incident light entering the Fabry-Perot etalon, and F is an intermediate physical quantity for obtaining the dispersed light beam and has no physical meaning.

[0012] Furthermore, the expression of the intermediate physical quantity F is: ; Wherein, R is the reflectivity of the anti-reflection coating of the Fabry-Perot etalon.

[0013] Compared with the prior art, the invention can achieve the following beneficial effects: The present invention creates the FP-based channel dispersion polarization spectrometer, adopts FP as the spectral dispersion element, avoids the low energy utilization of the grating dispersion spectrometer and the problem of spectral line bending in the prism dispersion, improves the energy utilization of the FP-based channel dispersion polarization spectrometer, and reduces the difficulty of later data processing. The present invention will play an important role in the structural design of the channel dispersion polarization spectroscopic imager and has a wide range of engineering application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The drawings constituting part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments and descriptions of the present invention are used to explain the present invention and do not constitute an improper limitation on the present invention. In the drawings: Figure 1 A schematic diagram of the structure of a channel dispersion polarization spectrometer based on FP according to an embodiment of the present invention; Figure 2 A schematic diagram of the structure of the polarization modulation module according to an embodiment of the present invention; Figure 3 A schematic diagram of the structure of the Fabry-Perot etalon according to an embodiment of the present invention; Figure 4 The present invention is a flowchart of a polarization spectrum measurement method of a channel dispersion polarization spectrometer based on FP described in an embodiment of the present invention.

[0015] Description of reference numerals: 1. Telescope objective lens; 2. Polarization modulation module; 3. Magnifying lens; 4. Fabry-Perot 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 DESCRIPTION

[0016] In order to make the purpose, technical solution and advantages of the invention more clear, the invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described here are only used to explain the invention and do not constitute a limitation of the invention.

[0017] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0018] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0019] In the description of the invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the invention can be understood according to specific circumstances.

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

[0021] like Figure 1As shown, a channel dispersion polarization spectrometer based on FP proposed by the present invention includes a telescope objective lens 1, a polarization modulation module 2, a magnifying lens 3, a Fabry-Perot etalon 4, an optical imaging lens 5 and a detector 6 arranged in sequence along the optical path direction, the telescope objective lens 1 obtains parallel light and makes the parallel light incident on the polarization modulation module 2; the polarization modulation module 2 generates a modulation spectrum curve, and modulates the polarization spectrum data of the parallel light to obtain a modulated light beam; the magnifying lens 3 adjusts the modulated light beam (so that the modulated light beam meets the incident angle requirement of the Fabry-Perot etalon 4), and makes the adjusted modulated light beam incident on the Fabry-Perot etalon 4; the Fabry-Perot etalon 4 performs spectral dispersion processing on the modulated light beam to obtain a dispersed light beam; the optical imaging lens 5 images the dispersed light beam on the detector 6; the detector 6 receives the dispersed light beam to obtain a polarization spectrum curve modulated by the Fabry-Perot etalon 4.

[0022] like Figure 2 As shown, the polarization modulation module 2 includes a first phase retarder 7, a second phase retarder 8 and a linear polarizer 9 arranged in sequence along the optical path direction, the thickness ratio of the first phase retarder 7 to the second phase retarder 8 is 1:2, and the fast axis direction of the first phase retarder 7 is 0°, the fast axis direction of the second phase retarder 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-Perot etalon 4 includes a first plate 10 and a second plate 11 which are sequentially arranged along the optical path direction. 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 close 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 reflectivity of 0.98. The material of the first plate 10 is quartz.

[0025] The detector 6 is a CMOS detector or a CCD detector.

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

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

[0028] The expression of the intermediate physical quantity F is: ; Here, R is the reflectivity of the anti-reflection film of the Fabry-Perot etalon 4 .

[0029] S3: The detector 6 receives the dispersed light beam and obtains a polarization spectrum curve modulated by the Fabry-Perot etalon 4.

[0030] S4: demodulating the polarization spectrum curve according to the radiation calibration coefficient of the channel dispersion polarization spectrometer to obtain the modulation spectrum curve generated by the polarization modulation module 2; performing Fourier transform processing on the modulation spectrum curve to obtain polarization spectrum data of the target to be measured.

[0031] For the FP-based channel dispersion polarization spectrometer, the light intensity obtained on the detector 6 and the input spectrum have the following relationship: , where DN is the number of electrons obtained by the detector 6, K is the radiation calibration coefficient, and I is the modulation spectrum curve generated by the polarization modulation module 2. After obtaining the modulation spectrum curve, the polarization spectrum data restoration method (Fourier transform, filtering, inverse Fourier transform) of the polarization modulation module 2 (PSIM) is used to obtain the polarization spectrum data of the target to be measured.

[0032] The present invention proposes a channel dispersion polarization spectrometer based on FP, and utilizes this structure to restore the polarization spectrum of the target light to be measured, which can effectively improve the energy utilization rate of the instrument (channel dispersion 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 the disclosure of the present invention can be performed in parallel, sequentially or in different orders, as long as the desired results of the technical solution disclosed in the present invention can be achieved, and this document does not limit this.

[0034] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A channel dispersion polarization spectrometer based on FP, characterized in that: The invention comprises a telescope objective lens, a polarization modulation module, a magnifying lens, a Fabry-Perot etalon, an optical imaging lens and a detector which are sequentially arranged along the optical path direction. The telescope objective lens obtains parallel light and makes the parallel light incident on 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 modulated light beam; the magnifying lens adjusts the modulated light beam and makes the adjusted modulated light beam incident on the Fabry-Perot etalon; the Fabry-Perot etalon performs spectral dispersion processing on the modulated light beam to obtain a dispersed light beam; the optical imaging lens images the dispersed light beam on the detector; the detector receives the dispersed light beam and obtains a polarization spectrum curve modulated by the Fabry-Perot etalon.

2. The FP-based channel dispersion 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 in sequence along the optical path direction, 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°.

3. The FP-based channel dispersion polarization spectrometer according to claim 1, characterized in that: The Fabry-Perot etalon comprises a first plate and a second plate arranged in sequence along the optical path direction, wherein the first plate and the second plate have the same structure and are arranged in parallel.

4. The FP-based channel dispersion polarization spectrometer according to claim 3, characterized in that: The wedge angle of the first plate is 30'. The first plate is coated with an anti-reflection film on one side close to the magnifying lens with a transmittance of 0.

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

98. The material of the first plate is quartz.

5. The FP-based channel dispersion polarization spectrometer according to claim 1, characterized in that: The detector is a CMOS detector or a CCD detector.

6. A method for measuring polarization spectrum of a channel dispersion polarization spectrometer based on FP, implemented by using the channel dispersion polarization spectrometer based on FP according to any one of claims 1 to 5, characterized in that: The specific steps include: S1: Aim the channel dispersion polarization spectrometer at the target to be measured, and the parallel light reflected by the target to be measured is incident on the polarization modulation module through the telescope objective lens. The polarization modulation module generates a modulation spectrum curve and modulates the polarization spectrum data of the parallel light to obtain a modulated light beam; S2: The lights of different wavelengths contained in the modulated light beam are incident on the Fabry-Perot etalon through the magnifying lens for coherent superposition to obtain a dispersed light beam; S3: The detector receives the dispersed light beam to obtain a polarization spectrum curve modulated by the Fabry-Perot etalon; S4: demodulating the polarization spectrum curve according to the radiation calibration coefficient of the channel dispersion polarization spectrometer to obtain the modulation spectrum curve generated by the polarization modulation module; performing Fourier transform processing on the modulation spectrum curve to obtain polarization spectrum data of the target to be measured.

7. The polarization spectrum measurement method of the FP-based channel dispersion polarization spectrometer according to claim 6, characterized in that: In step S1, the expression of the modulated light beam is: ； in, To modulate the beam, , , and is the Stokes vector of the polarization spectrum of the target to be measured, The amount of phase delay introduced by the polarization modulation module.

8. The polarization spectrum measurement method of the FP-based channel dispersion polarization spectrometer according to claim 6, characterized in that: In step S2, the transmittance expression of the dispersed light beam is: ； in, is the transmittance of the dispersed beam, is the thickness of the Fabry-Perot etalon, is the wavelength of the dispersed beam, is the incident angle of the incident light incident on the Fabry-Perot etalon, and F is an intermediate physical quantity for obtaining the dispersed light beam and has no physical meaning.

9. The polarization spectrum measurement method of the FP-based channel dispersion polarization spectrometer according to claim 8, characterized in that: The expression of the intermediate physical quantity F is: ； Wherein, R is the reflectivity of the anti-reflection coating of the Fabry-Perot etalon.

Images